[Federal Register Volume 70, Number 59 (Tuesday, March 29, 2005)]
[Rules and Regulations]
[Pages 15994-16035]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 05-6037]
[[Page 15993]]
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Part II
Environmental Protection Agency
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40 CFR Part 63
Revision of December 2000 Regulatory Finding on the Emissions of
Hazardous Air Pollutants From Electric Utility Steam Generating Units
and the Removal of Coal- and Oil-Fired Electric Utility Steam
Generating Units From the Section 112(c) List; Final Rule
Federal Register / Vol. 70, No. 59 / Tuesday, March 29, 2005 / Rules
and Regulations
[[Page 15994]]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 63
[OAR-2002-0056; FRL-7887-7]
RIN 2060-AM96
Revision of December 2000 Regulatory Finding on the Emissions of
Hazardous Air Pollutants From Electric Utility Steam Generating Units
and the Removal of Coal- and Oil-Fired Electric Utility Steam
Generating Units From the Section 112(c) List
AGENCY: Environmental Protection Agency (EPA).
ACTION: Final rule.
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SUMMARY: The EPA is revising the regulatory finding that it issued in
December 2000 pursuant to section 112(n)(1)(A) of the Clean Air Act
(CAA), and based on that revision, removing coal- and oil-fired
electric utility steam generating units (``coal- and oil-fired Utility
Units'') from the CAA section 112(c) source category list. Section
112(n)(1)(A) of the CAA is the threshold statutory provision underlying
today's action. That provision requires EPA to conduct a study to
examine the hazards to public health that are reasonably anticipated to
occur as the result of hazardous air pollutant (HAP) emissions from
Utility Units after imposition of the requirements of the CAA. The
provision also provides that EPA shall regulate Utility Units under
section 112, but only if the Administrator determines that such
regulation is both ``appropriate'' and ``necessary'' considering, among
other things, the results of the study. EPA completed the study in 1998
(the Utility Study), and in December 2000 found that it was
``appropriate and necessary'' to regulate coal- and oil-fired Utility
Units under CAA section 112. That December 2000 finding focused
primarily on mercury (Hg) emissions from coal-fired Utility Units. In
light of the finding, EPA in December 2000 announced its decision to
list coal- and oil-fired Utility Units on the section 112(c) list of
regulated source categories. In January 2004, EPA proposed revising the
December 2000 appropriate and necessary finding and, based on that
revision, removing coal- and oil-fired Utility Units from the section
112(c) list.
By this action, we are revising the December 2000 appropriate and
necessary finding and concluding that it is neither appropriate nor
necessary to regulate coal- and oil-fired Utility Units under section
112. We are taking this action because we now believe that the December
2000 finding lacked foundation and because recent information
demonstrates that it is not appropriate or necessary to regulate coal-
and oil-fired Utility Units under section 112. Based solely on the
revised finding, we are removing coal- and oil-fired Utility Units from
the section 112(c) list. The reasons supporting this action are
described in detail below. Other actions related to this final rule
include the recent promulgation of the final Clean Air Interstate Rule
(CAIR) and the final Clean Air Mercury Rule (CAMR).
DATES: Effective Date: The effective date of the final rule is March
29, 2005.
ADDRESSES: EPA has established a docket for this action under Docket ID
No. OAR-2002-0056. All documents in the docket are listed in the
EDOCKET index at http://www.epa.gov/edocket. Although listed in the
index, some information is not publicly available, i.e., Confidential
Business Information (CBI) or other information whose disclosure is
restricted by statute. Certain other material, such as copyrighted
material, is not placed on the Internet and will be publicly available
only in hard copy form. Publicly available docket materials are
available either electronically in EDOCKET or in hard copy at the EPA
Docket Center (EPA/DC), EPA West Building, Room B102, 1301 Constitution
Ave., NW., Washington, DC. The Public Reading Room is open from 8:30
a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The
telephone number for the Public Reading Room is (202) 566-1744, and the
telephone number for the EPA Docket Center is (202) 566-1742.
FOR FURTHER INFORMATION CONTACT: Ms. Wendy Blake, OGC Attorney, Office
of General Counsel, Environmental Protection Agency, (AR-2344),
Washington, DC 20460 telephone number: (202) 564-1821; fax number:
(202) 564-5603; e-mail address: [email protected].
Judicial Review. Pursuant to CAA section 307(b), judicial review of
this final rule is available only by filing a petition for review in
the United States Court of Appeals for the District of Columbia Circuit
by May 31, 2005. EPA designates this action a CAA section 307(d)
rulemaking. (See CAA section 307(d)(1)(V); 69 FR 4653 (January 30,
2004).) Under CAA section 307(d)(7)(B), only an objection to the rule
that was raised with reasonable specificity during the time period for
public comment can be raised during judicial review. Section
307(d)(7)(B) further provides that if the person raising the objection
can demonstrate to the Administrator that it was impracticable to raise
the objection during the public comment period or if the grounds for
the objection arose after the public comment period but within the time
period specified for judicial review and if the objection is of central
relevance, EPA will convene a proceeding for reconsideration of the
rule and provide the same procedural rights as would have been afforded
had the information been available at the time the rule was proposed.
I. Statutory Background
In the 1990 Amendments to the CAA, Congress substantially modified
CAA section 112, the provision of the CAA addressing HAP. Among other
things, section 112 contains a list of ``hazardous air pollutants,''
which are ``pollutants which present, or may present, * * * a threat of
adverse human health effects * * * or adverse environmental effects
whether through ambient concentrations, bioaccumulation, deposition, or
otherwise.'' (See CAA section 112(b)(2).) In the 1990 amendments to the
CAA, Congress listed 190 HAP, and authorized EPA to add or remove
pollutants from the list.\1\ (See CAA Section 112(b)(1)-(b)(3).)
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\1\ The current section 112(b) list includes 188 HAP.
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The types of sources addressed under section 112 include: major
sources, area sources, and electric utility steam generating units
(Utility Units). (See CAA 112(a)(1), (a)(2), (a)(8).) A ``major
source'' is any stationary source \2\ or group of stationary sources at
a single location and under common control that emits or has the
potential to emit ten tons or more per year of any HAP or 25 tons or
more per year of any combination of HAP. (See CAA 112(a)(1).) A
stationary source of HAP that is not a ``major source'' is an ``area
source.'' (See CAA 112(a)(2).) Finally, an electric utility steam
generating unit is any ``fossil fuel fired combustion unit of more than
25 megawatts that serves a generator that produces electricity for
sale.'' (See CAA 112(a)(8).)
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\2\ A ``stationary source'' of hazardous air pollutants is any
building, structure, facility or installation that emits or may emit
any air pollutant. (See CAA Section 111(a)(3) and 112(a)(3).)
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There are two important steps under section 112: (1) Determining
whether a source category meets the statutory criteria for regulation
under section 112; and (2) promulgating emission standards for those
source categories regulated under section 112. In terms of the first
step, Congress required EPA to publish a list of categories and
[[Page 15995]]
subcategories of major sources and area sources by November 15,
1991.\3\ (See CAA 112(c)(1) & (c)(3).) Congress further directed EPA to
revise this initial list periodically, based on, for example, new
information. (See 112(c)(1).) EPA is required to list a category of
major sources under section 112(c)(1) if at least one stationary source
in the category meets the definition of a major source--i.e., if a
certain amount of a HAP (or combination of HAP) is emitted from the
source. (See 112(a)(1).) By contrast, EPA is required to list
categories or subcategories of area sources only if they meet one of
the following statutory criteria: (1) EPA determines that the category
of area sources presents a threat of adverse effects to human health or
the environment that warrants regulation under CAA section 112; or (2)
the category of area sources falls within the purview of CAA section
112(k)(3)(B) (the Urban Area Source Strategy). (See CAA 112(c)(3).)
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\3\ EPA published the initial list on July 16, 1992. See 57 FR
31,576, July 16, 1992. EPA did not include Utility Units on the
initial section 112(c) list because Congress required EPA to conduct
and consider the results of the study required by section
112(n)(1)(A) before regulating these units and, therefore, listing
in 1992 was not authorized by statute.
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For those source categories regulated under section 112, the next
step concerns the establishment of emission standards. Under section
112(d), EPA must establish emission standards that ``require the
maximum degree of reduction in emissions of the hazardous air
pollutants subject to this section'' that the Administrator determines
is achievable based on technology, taking into account certain factors
such as cost, energy requirements, and other impacts. The emission
standard for new sources cannot be, however, less stringent than the
level of control achieved by the best controlled similar source, and
the emission standard for existing sources cannot be less stringent
than the average emission limitation achieved by the best performing 12
percent of existing sources in the category, regardless of cost, energy
requirements and other impacts. CAA 112(d)(2) and (3). Finally, within
eight years after promulgation of section 112(d) emission standards for
a listed source category, EPA must promulgate additional standards if
such standards are necessary to provide an ample margin of safety to
protect public health or to prevent an adverse environmental effect.
(See CAA section 112(f).) These additional standards under CAA section
112(f) are commonly referred to as ``residual risk'' standards.
The criteria for listing major and area sources established in
section 112(c)(1) and (c)(3) do not apply to Utility Units because
Congress treated Utility Units differently from other major and area
sources. Indeed, Congress enacted a special provision for Utility Units
in section 112(n)(1)(A), which governs whether Utility Units should
even be regulated under section 112.\4\ Section 112(n)(1)(A) directs
EPA to conduct a study to evaluate what ``hazards to public health
[are] reasonably anticipated to occur'' as the result of HAP emissions
from Utility Units ``after imposition of the requirements of th[e]
Act,'' (emphasis added) and to report the results of such study to
Congress by November 15, 1993. Congress also directed EPA to describe
in the report to Congress ``alternative control strategies for [those]
emissions that may warrant regulation under this section.'' (See CAA
section 112(n)(1)(A).) Section 112(n)(1)(A) further provides that EPA
shall regulate Utility Units under section 112 if the Administrator
determines, considering the results of the study, that such regulation
is ``appropriate and necessary.'' Thus, unlike other major and area
sources, Congress first required EPA to examine how ``imposition of the
requirements of th[e] Act'' would affect the overall level of utility
HAP emissions, and then determine whether regulation of Utility Units
under section 112 is both appropriate and necessary. Section
112(n)(1)(A) therefore sets an important and unique condition precedent
for regulating Utility Units under section 112 and provides EPA
discretion in determining whether that condition precedent has been
met.
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\4\ No one would dispute that certain Utility Units would meet
the definition of a ``major source'' based on the quantity of HAP
emitted from such units, or that other Utility Units may meet the
``area source'' criteria for listing under section 112(c)(3), but
Congress recognized this fact in 1990 and specifically enacted
section 112(n)(1)(A), which establishes an entirely different test
for determining whether Utility Units should be regulated under
section 112.
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II. Regulatory Background
A. EPA's December 20, 2000 Regulatory Finding
On December 20, 2000, EPA issued a finding pursuant to CAA section
112(n)(1)(A) that it was appropriate and necessary to regulate coal-
and oil-fired Utility Units under section 112. In making that finding,
EPA considered the Utility Study, which was completed and submitted to
Congress in February 1998.
In the Utility Study, we divided Utility Units into three
subcategories based on fuel type: coal-, oil-, and gas-fired units. We
then analyzed HAP emissions from each subcategory. We followed this
approach because each subcategory burns a different fuel, which, in
turn, leads to different emissions profiles, which can require
different emission controls. This approach is also consistent with
EPA's historical practice of subcategorizing Utility Units based on
fuel type. (See, e.g., 40 CFR 60.44(a).)
Because EPA subcategorized Utility Units for purposes of the
Utility Study, EPA, in December 2000, made separate ``appropriate and
necessary'' findings under section 112(n)(1)(A) for gas-fired, coal-
fired, and oil-fired Utility Units. In making these findings, EPA
considered the Utility Study and certain additional information
obtained after completion of the Utility Study, including the National
Academy of Sciences' report concerning the health effects of
methylmercury and actual emissions data obtained in response to an
information collection request EPA issued to all coal-fired Utility
Units in 1999. See 65 FR 79826. EPA reasonably relied on this
additional information because the information provided a more
comprehensive and contemporaneous record concerning Hg emissions from
coal-fired units. Nothing in section 112(n)(1)(A) suggests that
Congress sought to preclude EPA from considering more current
information in making the appropriate and necessary finding.
In the December 2000 finding, EPA determined that it was
appropriate and necessary to regulate coal- and oil-fired units, but
not gas-fired units.\5\ With respect to the latter, EPA found that
regulation of HAP emissions from natural gas-fired Utility Units ``is
not appropriate or necessary because the impacts due to HAP emissions
from such units are negligible based on the results of the study
documented in the utility RTC.'' (Emphasis added) See 65 FR 79831.
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\5\ Although the December 2000 finding addressed three
subcategories of Utility Units--coal-, oil-, and gas-fired units,
the majority of the finding concerned Hg emissions from coal-fired
power plants. 65 FR 79826-29 (explaining that Hg from coal-fired
units is the HAP of greatest concern); Utility Study, ES-27
(``mercury from coal-fired utilities is the HAP of greatest
potential concern.'').
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EPA provided three primary reasons in support of its finding that
it was ``appropriate'' to regulate coal- and oil-fired Utility Units
under section 112. First, EPA found that it was appropriate to regulate
HAP emissions from coal- and oil-fired Utility Units because Utility
Units ``are the largest domestic source of Hg emissions.'' See 65 FR
79830. EPA next found that it was
[[Page 15996]]
appropriate to regulate coal- and oil-fired Utility Units because
``mercury in the environment presents significant hazards to public
health and the environment.'' \6\ See 65 FR 79830. Finally, EPA
explained that it was appropriate to regulate HAP emissions from coal-
and oil-fired units because it had identified certain control options
that, it anticipated, would effectively reduce HAP from such units. In
discussing the appropriate finding, EPA also noted that uncertainties
remained concerning the extent of the public health impact from HAP
emissions from oil-fired units. Thus, EPA's determination that it was
``appropriate'' to regulate coal- and oil-fired units under section 112
hinged on the health effects associated with Hg emissions from coal-
fired Utility Units, the uncertainties associated with the health
effects of HAP from oil-fired Utility Units, and EPA's belief that
control options would be available to reduce certain utility HAP
emissions.\7\
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\6\ Section IV below addresses our conclusion that it is not
appropriate and necessary to regulate coal- and oil-fired Utility
Units under section 112 and explains why we now believe that our
December 2000 finding lacked foundation. As explained below, one of
the reasons the December 2000 ``appropriate'' finding for oil-fired
Utility Units lacks foundation is because the record that was before
the Agency in December 2000 establishes that Hg is a HAP of concern
only as emitted from coal-fired units, not oil-fired units. Utility
Study ES-5,13,27. EPA therefore should not have relied upon Hg
emissions as a basis for finding it was appropriate to regulate oil-
fired units under section 112. (See, e.g., Utility Study ES-5, ES-
27.)
\7\ The ``appropriate'' finding for oil-fired units stemmed
primarily from EPA's concerns over the potential health effects of
nickel from such units. As explained in the January 2004 proposed
rule, the record before the Agency in December 2000 supported a
distinction between nickel and the other HAP emitted from oil-fired
units. See 69 FR 4688. We proposed that this distinction was
reasonable based on the relative amount of nickel emitted from oil-
fired units and the health effects associated with such emissions.
(See also Utility Study at ES-12 (noting higher population
concentrations surrounding oil-fired units). At the time of the
proposed rule, we recognized, however, the uncertainties in the data
underlying our ``appropriate'' finding for oil-fired units based on
nickel emissions, and for that reason solicited information as to
whether nickel emissions from oil-fired plants currently pose a
hazard to public health.
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Once EPA determined that it was ``appropriate'' to regulate coal-
and oil-fired Utility Units under section 112 of the CAA, EPA next
concluded that it was also ``necessary'' to regulate HAP emissions from
such units under section 112. Interpreting the term ``necessary'' in
section 112(n)(1)(A), EPA found that it was necessary to regulate HAP
from coal- and oil-fired Utility Units ``because the implementation of
other requirements under the CAA will not adequately address the
serious public health and environmental hazards arising from such
emissions identified in the Utility RTC.'' See 65 FR 79830.
In light of the positive appropriate and necessary determination,
EPA in December 2000 listed coal- and oil-fired Utility Units on the
section 112(c) source category list. See 65 FR 79831 (our finding that
it is appropriate and necessary to regulate coal- and oil-fired Utility
Units under section 112 ``adds these units to the list of source
categories under section 112(c).''). Relying on CAA section 112(e)(4),
EPA explained in its December 2000 finding that neither the appropriate
and necessary finding under section 112(n)(1)(A), nor the associated
listing were subject to judicial review at that time. EPA did not add
natural-gas fired units to the section 112(c) list in December 2000
because it did not make a positive appropriate and necessary finding
for such units.
B. Litigation Challenging December 2000 Regulatory Finding
Shortly after issuance of the December 2000 Finding, an industry
group challenged the December 2000 finding in the United States Court
of Appeals for the District of Columbia Circuit (DC Circuit). UARG v.
EPA, 2001 WL 936363, No. 01-1074 (DC Cir. July 26, 2001). EPA moved to
dismiss the lawsuit on the basis of section 112(e)(4), which provides,
in pertinent part, that ``no action of the Administrator * * * listing
a source category or subcategory under subsection (c) of this section
shall be a final agency action subject to judicial review, except that
any such action may be reviewed under such section 7607 of this title
when the Administrator issues emission standards for such pollutant or
category.'' (Emphasis added.) (See CAA Section 112(e)(4).)
In its motion to dismiss the petition, EPA argued to the DC
Circuit, among other things, that the December 2000 listing of coal-
and oil-fired Utility Units was inseparable from the appropriate and
necessary finding and that the appropriate and necessary finding and
listing actions are not final agency actions pursuant to section
112(e)(4). See also 65 FR 79826. EPA further noted in its motion to
dismiss that both the finding and the listing would be subject to
additional notice and comment as part of the section 112(d) rulemaking.
See EPA's Motion to Dismiss, UARG v. EPA, 2001 WL 936363, No. 01-1074S
(``Because the decision to add coal and oil fired electric utility
steam generating units to the source category list is not yet final
agency action, it will be among the matters subject to further comment
in the subsequent [standards] rulemaking.''); 65 FR 79831 (noting that
issues related to the listing, such as ``the exact dimension of the
source category,'' will be subject to additional comment in the
emission standard rulemaking process). The DC Circuit dismissed the
challenge to the December 2000 finding for lack of jurisdiction based
on section 112(e)(4) of the CAA. The December 2000 finding and
associated listing are therefore not final agency actions.
C. January 30, 2004 Proposed Rule and March 2004 Supplemental Notice
On January 30, 2004, EPA published in the Federal Register a
proposed rule entitled ``Proposed National Emissions Standards for
Hazardous Air Pollutants; and, in the Alternative, Proposed Standards
of Performance for New and Existing Stationary Sources: Electric
Utility Steam Generating Units.'' (See 69 FR 4652 (January 30, 2004).)
In that rule, EPA proposed three alternative regulatory approaches.
First, EPA proposed to retain the December 2000 Finding and associated
listing of coal- and oil-fired Utility Units and to issue under section
112(d) maximum achievable control technology-based (MACT) emission
standards for both subcategories. Second, EPA alternatively proposed
revising the Agency's December 2000 Finding, removing coal and oil-
fired Utility Units from the section 112(c) list,\8\ and issuing final
standards of performance under CAA section 111 for new and existing
coal-fired units that emit Hg and new and existing oil-fired units that
emit nickel. Finally, as a third alternative, EPA proposed retaining
the December 2000 finding, removing coal and oil-fired Utility Units
from the section 112(c) list, and regulating Hg emissions from Utility
Units under CAA section 112(n)(1)(A).
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\8\ We did not propose revising the December 2000 finding for
gas-fired Utility Units because EPA continues to believe that
regulation of such units under section 112 is not appropriate and
necessary. We have not received any information that would cause us
to change our conclusion in this regard. In fact, the information
that we have received since the Utility Study only confirms the
conclusion we reached in December 2000. We therefore take no action
today with regard to the December 2000 finding for gas-fired Utility
Units.
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Shortly thereafter, on March 16, 2004, EPA published in the Federal
Register a supplemental notice of proposed rulemaking entitled
``Supplemental Notice of Proposed National Emission Standards for
Hazardous Air Pollutants; and, in the Alternative, Proposed Standards
of Performance for New and Existing Stationary Sources: Electric
Utility Steam Generating Units.'' See 69 FR 13298 (March 16, 2004). In
that
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notice, EPA proposed certain additional regulatory text, which largely
governed the proposed section 111 standards of performance for Hg,
which included a cap-and-trade program. The supplemental notice also
proposed state plan approvability criteria and a model cap-and-trade
rule for Hg emissions from coal-fired Utility Units. The Agency
received thousands of comments on the proposed rule and supplemental
notice.\9\ Comments relating to the central issues concerning today's
action are addressed in this preamble. The remainder of our responses
are contained in the response to comments document which is in the
docket.\10\
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\9\ We initially estimated that we had over 680,000 submissions
from the public on the proposed rule and the supplemental notice,
which came primarily in the form of letters and e-mails. A recent
review of the electronic docket reveals that our initial estimate
was over-stated. The docket reflects approximately 500,000 separate
submissions from the public, about 5,000 of which represent unique
comments.
\10\ The response to comments document relevant to this rule is
called: ``Response to Significant Public Comments Concerning the
Proposed Revision of the December 2000 Appropriate and Necessary
Finding and Proposed Removal of Utility Units From the Section
112(c) List.''
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D. The December 2004 Notice of Data Availability
On December 1, 2004, EPA published in the Federal Register a notice
of data availability entitled ``Proposed National Emission Standards
for Hazardous Air Pollutants; and, in the Alternative, Proposed
Standards of Performance for New and Existing Stationary Sources,
Electric Utility Steam Generating Units: Notice of Data Availability.''
See 69 FR 69864 (December 1, 2004). EPA issued this notice to seek
additional information and input concerning: (1) Certain Hg data and
information that the Agency received in response to the proposed rule
and supplemental notice, (2) the different forms of Hg that are emitted
into the atmosphere from coal-fired Utility Units and how those forms
respond to different control technologies; and (3) a revised proposed
benefits methodology for assessing the benefits of Hg regulation. The
benefits methodology generally involves analyzing Hg emissions from
coal-fired Utility Units, conducting deposition modeling based on the
identified Hg emissions, and relating that deposition modeling to
methylmercury concentrations in fish. EPA conducts benefits analyses
for rulemakings consistent with the provisions of Executive Order
12866.
III. EPA's Interpretation of CAA Section 112(n)(1)(A)
As explained above, Congress treated Utility Units differently from
other major and area sources and provided EPA considerable discretion
in evaluating whether to regulate Utility Units under section 112.
Section 112(n)(1)(A) provides, in full:
The Administrator shall perform a study of the hazards to public
health reasonably anticipated to occur as a result of emissions by
electric utility steam generating units of pollutants listed under
subsection (b) of this section after imposition of the requirements
of this Act. The Administrator shall report the results of this
study to the Congress within 3 years after the date of the enactment
of the Clean Air Act Amendments of 1990. The Administrator shall
develop and describe in the Administrator's report to Congress
alternative control strategies for emissions which may warrant
regulation under this section. The Administrator shall regulate
electric utility steam generating units under this section, if the
Administrator finds such regulation is appropriate and necessary
after considering the results of the study required by this
subparagraph.
(Emphasis added.).
The italicized terms in the above paragraph are central terms in
section 112(n)(1)(A). Before we address our interpretation of these
terms, however, we again summarize the requirements of section
112(n)(1)(A). The first step under section 112(n)(1)(A), which is
addressed by the first three sentences of section 112(n)(1)(A),
concerns the completion of a study and submission of the results of
that study to Congress by November 15, 1993. The study is to examine
the hazards to public health from utility HAP emissions that are
reasonably anticipated to occur following imposition of the
requirements of the CAA and to identify alternative control strategies
for those HAP that may warrant regulation under section 112. The second
step, which is addressed by the last sentence of section 112(n)(1)(A),
requires EPA to determine whether regulation of Utility Units under
section 112 is appropriate and necessary considering, among other
things, the results of the study. Congress provided no deadline by
which this determination must be made.
Section 112(n)(1)(A) itself contains no clear standard to govern
EPA's analysis and determination of whether it is ``appropriate and
necessary'' to regulate utilities under section 112. The first sentence
of the subparagraph describes the scope of the study EPA was to
conduct. The sentence on EPA's ``appropriate and necessary'' finding
then says that the Agency must make that finding after considering the
results of the study. But Congress did not supply an actual definition
or test for determining whether regulation of utilities under section
112 is ``appropriate and necessary.'' Thus, EPA must supply a
reasonable interpretation of those terms to fill the gap. Chevron USA
Inc. v. NRDC, 467 U.S. 837 (1984).
Congress' direction on the study provides the only guidance in
section 112(n)(1)(A) about the substance of EPA's inquiry. Because the
statute provides no other explicit guidance, EPA has chosen to
extrapolate from Congress' description of the study to adopt a
reasonable interpretation of the phrase ``appropriate and necessary.''
The following sections describe how the Agency has used Congress'
guidance on the study to formulate different aspects of our
interpretation and application of the ``appropriate and necessary''
test.
A. Hazards to Public Health Reasonably Anticipated To Occur
In section 112(n)(1)(A), Congress directed EPA to perform a study
of ``hazards to public health'' that would likely result from utility
HAP emissions, before making any further decisions about regulating
utilities under section 112. Unlike other sections of the CAA, section
112(n)(1)(A) focuses only on hazards to public health. It does not
require that EPA study other factors, such as environmental effects
without any established pathways to human health effects. In contrast,
section 112(n)(1)(B) requires a separate EPA study, although not as a
precursor to a regulatory determination, of the ``health and
environmental effects'' of ``mercury emissions'' from a broad range of
sources. Also unlike Section 112(n)(1)(A), many of the other
requirements of section 112 explicitly require both an assessment of
human health effects and, in addition, an assessment of adverse
environmental effects. For example, the Administrator is charged with
periodically reviewing the list of Hazardous Air Pollutants and adding
pollutants that present a threat of either ``adverse human health
effects'' or ``adverse environmental effects.'' CAA Section 112(b)(2).
The Administrator examines area sources of HAPs to determine if they
present ``a threat of adverse effects to human health or the
environment.'' CAA Section 112(c)(3). The Administrator is to
prioritize action under section 112(d) after considering ``the known or
anticipated adverse effects of such pollutants on public health and
environment.'' CAA Section 112(e)(2)(A). Nor did Congress appear to
view the two terms as synonymous. Under section 112(f), the EPA
[[Page 15998]]
promulgates emission standards at a level ``with an ample margin of
safety'' to ``protect public health.'' CAA Section 112(f)(2)(A). The
Administrator may go further and impose more stringent standards to
protect against ``an adverse environmental effect'' only after
considering ``cost, energy, safety, and other relevant factors.'' Id.
As described above, section 112(n)(1)(A) also provides no clear
standard for analyzing public health effects--in contrast to, for
example, section 112(f). Under section 112(f), the issue is whether
additional regulation is needed to ``provide an ample margin of safety
to protect public health.'' Section 112(f) also expressly incorporates
EPA's pre-1990 two-part inquiry for evaluating what level of emission
reduction is needed to provide an ample margin of safety to protect
public health. See CAA section 112(f)(2)(B) (incorporating EPA's two-
part ample margin of safety inquiry, set forth at 54 FR 38044 September
14, 1989, which implemented the requirements of section 112 of the 1977
CAA).\11\ By contrast, section 112(n)(1)(A) neither includes the
``ample margin of safety to protect public health'' requirement, nor
does it incorporate EPA's pre-1990 ample margin of safety inquiry.
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\11\ Section 112 of the 1977 CAA directed EPA to promulgate
emission standards ``at the level which in * * * [the
Administrator's judgment] provides an ample margin of safety to
protect the public health.'' Congress substantially amended section
112 in 1990 and enacted several new provisions. Congress
specifically incorporated the ``ample margin of safety to protect
public health'' requirement into section 112(f), which applies to
any source category that is regulated under section 112(d)(2) and
(d)(3). Significantly, Congress did not include the ``ample margin
of safety'' language in section 112(n)(1)(A). Instead, Congress
directed EPA to assess the ``hazards to public health reasonably
anticipated to occur'' from utility HAP emissions after imposition
of the requirements of the CAA, and then determine whether Utility
unit emissions should be regulated under section 112 of the CAA.
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Because of the focus on ``public health'' in the section
112(n)(1)(A) study requirement, and because as discussed above Congress
did not define the scope of the ``appropriate and necessary'' finding,
EPA is reasonably interpreting section 112(n)(1)(A) to base that
finding on an assessment of whether utility HAP emissions likely would
result in ``hazards to public health.''
Moreover, EPA reasonably interprets section 112(n)(1)(A) not to
require the Agency either to study or to base its ``appropriate and
necessary'' finding on an assessment of environmental effects unrelated
to public health.
As described above, Section 112(n)(1)(A) requires only that the
Administrator ``consider'' the results of the public health study
before determining whether utility regulation is ``appropriate and
necessary.'' This mild direction, when paired with the considerable
discretion inherent in any judgment about whether an action is
``appropriate and necessary,'' has led EPA to conclude that the statute
permits the agency to consider other relevant factors when determining
whether to regulate emissions from utility units under section 112.
This is not to say, however, that EPA believes it may ignore the
context of section 112(n) in making its determination.
The Supreme Court has recognized that ``where Congress includes
particular language in one section of a statute but omits it in another
section of the same Act,'' as here, where section 112(n)(1)(A) refers
to public health and conspicuously omits any reference to adverse
environmental effect, ``it is generally presumed that Congress acts
intentionally * * * in the disparate inclusion or exclusion.'' Russello
v. United States, 464 U.S. 16, 23 (1983). The only direction that
Congress explicitly provided to guide our ``appropriate and necessary''
finding was that we consider the results of a study of only those
``hazards to public health'' that the agency ``reasonably anticipate[s]
to occur.''
EPA must reconcile the broad discretion to determine what is
``appropriate and necessary'' with the implicit Congressional decision
that information about environmental effects unrelated to human health
effects was not needed for that determination. Rather than conclude
that EPA is prohibited from considering environmental effects, however,
EPA interprets section 112(n)(1)(A) to permit the agency to consider
other relevant factors as part of its ``appropriate and necessary''
determination, as refined further below, but these factors may not
independently, or in conjunction with one another, justify regulation
under section 112(n) when EPA has concluded that hazards to U.S. public
health are not reasonably anticipated to occur. Compare CAA section
112(f)(2)(A) (Administrator may set a more stringent standard than is
required to protect health if necessary, considering factors such as
cost, to prevent an adverse environmental effect).
In evaluating hazards to public health under section 112(n)(1)(A)
we look at various factors, including, for example, the affected
population, the characteristics of exposure (e.g., level and duration),
the nature of the data, including the uncertainties associated with the
data, and the nature and degree of health effects. In terms of
assessing health effects, we have numerous tools at our disposal. See
Section VI.H (for fuller discussion of factors relevant to assessing
the hazards to public health). For example, for cancer effects, we can
assess the lifetime excess cancer risk, and for other effects, we look
to tools, such as the reference dose.\12\ As explained below, the
``hazards to public health reasonably anticipated to occur'' standard
is relevant not only for the Study, but also for the appropriate and
necessary determination.
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\12\ Section VI below discusses the reference dose (``RfD'') in
detail.
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EPA has also taken note of the context for assessing ``hazards to
public health,'' for the language of section 112(n)(1)(A), calls for an
analysis of the ``hazards to public health'' reasonably anticipated to
``occur as a result of emissions by electric utility steam generating
units.'' (Emphasis added.) Section 110(a)(2)(D) provides an instructive
comparison in this regard. In section 110(a)(2)(D), Congress required
that each state implementation plan contain adequate provisions
``prohibiting * * * any source or other type of emissions activity
within the State from emitting any air pollutant in amounts'' that will
``contribute significantly to nonattainment'' of the national ambient
air quality standards. This provision demonstrates that Congress knew
how to require regulation of emissions of air pollutants even where the
pollutants themselves do not cause a problem, but rather only
``contribute to a problem.'' Unlike section 110(a)(2)(D), in section
112(n)(1)(A), Congress focused exclusively on the ``hazards to public
health'' of HAP emissions ``result[ing] from'' Utility Units. Rather,
it is the EPA study performed pursuant to section 112(n)(1)(B), not the
inquiry under section 112(n)(1)(A), that examines all current
anthopogenic sources of Hg emissions and their effects on human health
and the environment. EPA has concluded that its inquiry under section
112(n)(1)(A) may reasonably focus solely on whether the utility HAP
emissions themselves are posing a hazard to public health. This focus
on utility emissions only is consistent with Congress' overall decision
to provide for separate treatment of utilities in section 112(n)(1)(A).
B. Imposition of the Requirements of This Act
Congress required EPA to examine the hazards to public health from
utility emissions ``after imposition of the requirements of this Act.''
The phrase ``imposition of the requirements of th[e] Act'' is
susceptible to different
[[Page 15999]]
interpretations because Congress did not specify the scope of the
requirements under the CAA to be considered or, more importantly, the
time period over which the imposition of requirements was to be
examined. EPA reasonably interprets the phrase ``imposition of the
requirements of th[e] Act'' to include not only those requirements
already imposed and in effect, but also those requirements that EPA
reasonably anticipates will be implemented and will result in
reductions of utility HAP emissions. This interpretation is reasonable
in view of the fact that Congress called for the study to be completed
within three years of enactment of the 1990 CAA Amendments. At such
time, EPA could have only forecast, to the extent possible, how
implementation of the requirements of the CAA would impact utility HAP
emissions, based on the science and the state of technology at the
time.\13\
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\13\ Although the December 2000 finding does not provide an
interpretation of the phrase ``after imposition of the requirements
of the[e] Act,'' the Utility Study, on which that finding was based,
does account for the phrase by evaluating utility HAP emission
levels in 2010. See Utility Study ES-2 (the ``2010 scenario was
selected to meet the section 112(n)(1)(A) mandate to evaluate
hazards `after imposition of the requirements of 'the CAA.''). We do
not believe that the December 2000 finding or the January 2004
proposal properly give effect to all of the terms of section
112(n)(1)(A), including the first sentence of section 112(n)(1)(A).
We therefore provide our interpretation of the central terms in that
sentence above, as those terms are relevant to the final actions we
are taking today.
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We are interpreting the phrase ``requirements of th[e] Act''
broadly to include CAA requirements that could either directly or
indirectly result in reductions of utility HAP emissions. For example,
certain provisions of the CAA that affect Utility Units, such as the
requirements of Title I and Title IV, require controls on pollutants
like SO2 or NOX. Although these pollutants are
not HAP, the controls that are required to achieve the needed
reductions have the added effect of reducing HAP emissions. Thus, given
our interpretation of the phrase ``imposition of the requirements of
th[e] Act,'' we read the first sentence of section 112(n)(1)(A) as
calling for a study of the hazards to public health from utility HAP
emissions that EPA reasonably anticipates would occur after
implementation of the CAA requirements that EPA, at the time of the
study, should have reasonably anticipated would be implemented and
would directly or indirectly result in reductions of utility HAP
emissions.
Finally, it is telling that Congress directed EPA to examine the
utility HAP emissions remaining ``after imposition of the requirements
of th[e] Act,'' because there is no other provision in section 112 that
calls for EPA to examine the requirements of the CAA in assessing
whether to regulate a source category under section 112.\14\ Congress
plainly treated Utility Units differently from other source categories,
and that special treatment reveals Congress' recognition that Utility
Units are a broad, diverse source category that is subject to numerous
CAA requirements, including requirements under both Title I and Title
IV, and that such sources should not be subject to duplicative or
otherwise inefficient regulation.\15\ See 136 Cong. Rec. H12911, 12934
(daily ed. Oct. 26, 1990) (Statement of Congressman Oxley) (stating
that the conferees adopted section 112(n)(1)(A) ``because of the logic
of basing any decision to regulate on the results of scientific study
and because of the emission reductions that will be achieved and the
extremely high costs that electric utilities will face under other
provisions of the new Clean Air Act amendments.'').
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\14\ Section 112(m)(6) provides an instructive comparison
because it requires EPA to examine the other provisions of section
112, and to determine whether those provisions are adequate to
prevent serious adverse effects to public health and the environment
associated with atmospheric deposition to certain waterbodies.
Section 112(m)(6) also requires EPA to promulgate additional
regulations setting emission standards or control requirements, ``in
accordance with'' section 112 and under the authority of section
112(m)(6), if EPA determines that the other provisions of section
112 are adequate, and such regulations are appropriate and necessary
to prevent serious adverse public health and environmental effects.
Section 112(n)(1)(A) provides EPA far greater discretion because
under that section, EPA is not only to evaluate the reasonably
anticipated public health hazards remaining ``after imposition of
the requirements of th[e] Act,'' but also to determine whether to
regulate Utility Units under section 112 of the CAA at all.
\15\ As noted elsewhere, section 112(n)(1)(A) was included in
the House Committee bill and adopted by the House; while the Senate
included a different provision. In the Conference Committee, the
House version prevailed. Sen. Durenberger, a Senate conferee and an
evident opponent of the provision, alluded to another purpose for
the provision, which concerns the fact that ``mercury is a global
problem.'' Legislative History of the Clean Air Act Amendments of
1990, at 872 (Oct. 27, 1990) (statement of Sen. Durenberger). Based
on Sen. Durenberger's statement, it appears that one of the reasons
for the wide deference Congress accorded EPA under section
112(n)(1)(A) was to allow EPA to account for the fact that Hg
emissions from U.S. utilities are a very small part of overall Hg
emissions, and therefore that EPA should exercise discretion in
considering the uncontrollable amount of risk from Hg that would
remain regardless of the extent to which U.S. utilities are
controlled.
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C. Appropriate and Necessary After Considering the Results of the Study
Section 112(n)(1)(A) requires EPA to make a determination as to
whether regulation of Utility Units under section 112 is ``appropriate
and necessary.'' Congress did not define the terms ``appropriate'' and
``necessary,'' but provided that regulation of Utility Units under
section 112 could occur only if EPA determines that such regulation is
both ``appropriate'' and ``necessary.''
1. Considering the Results of the Study
The appropriate and necessary determination is to be made only
after ``considering the results of the study'' required under section
112(n)(1)(A). We interpret the phrase ``considering the results of the
study'' to mean that EPA must consider the results of the study in
making its determination, but that EPA is not foreclosed from analyzing
other relevant information that becomes available after completion of
the study. This interpretation is reasonable because section
112(n)(1)(A) contains no deadline by which EPA must determine whether
it is ``appropriate and necessary'' to regulate Utility Units under
section 112.
Moreover, nothing in section 112(n)(1)(A) suggests that EPA is
precluded from considering new relevant information obtained after
completion of the Utility Study in determining whether regulation of
Utility Units under section 112 is appropriate and necessary. Indeed,
the term ``considering'' in section 112(n)(1)(A) is analogous to the
terms ``based on'' or ``including,'' which are neither limiting nor
exclusive terms.\16\ In a recent case, the DC Circuit rejected an
argument advanced by the petitioners that an EPA rule was invalid
because the statute required EPA to promulgate the regulation ``based
on the study,'' and according to petitioners EPA's rule was not based
on a study that met the requirements of the CAA. Sierra Club v. EPA,
325 F.3d 374 (DC Cir. 2003). In rejecting petitioners' arguments, the
Court held, among other things, that ``the statute doesn't say that the
rule must be based exclusively on the study.'' Sierra Club v. EPA, 325
F.3d at 377 (emphasis in original); See also United States v. United
Technologies Corp., 985 F.2d 1148, 1158 (2d Cir. 1993) (``based upon''
does not mean ``solely''); McDaniel v. Chevron Corp., 203 F.3d 1099,
1111 (9th Cir. 2000). Consistent with this reasoning, EPA reasonably
interprets the phrase ``considering the results of the study,'' to mean
that EPA must consider the study, but that it can consider other
relevant information obtained after completion of the study. Congress
could not have reasonably intended for EPA to
[[Page 16000]]
ignore relevant information concerning HAP emissions from Utility Units
solely because that information was obtained after completion of the
Utility Study.\17\
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\16\ In fact, the term ``considering,'' on its face, is less
limiting than the phrase ``based on.''
\17\ Consistent with this interpretation, in December 2000, EPA
relied not only on the Utility Study, but also on certain
information concerning Hg obtained after completion of the study,
including actual emissions data from coal-fired plants for calendar
year 1999 and a report from the National Academy of Sciences on the
health effects of methylmercury. See 65 FR 79825-27.
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2. Appropriate and Necessary
The condition precedent for regulating Utility Units under section
112 is whether such regulation is ``appropriate'' and ``necessary.''
These are two very commonly used terms in the English language, and
Congress has not ascribed any particular meaning to these terms in the
CAA. The legislative history does not resolve Congress' intent with
regard to these terms. We therefore first examine the structure of
section 112(n)(1)(A) and then discuss our interpretation of the terms
``appropriate'' and ``necessary.''
a. Examining the Structure of Section 112(n)(1)(A). In interpreting
the terms ``appropriate'' and ``necessary'' in section 112(n)(1)(A), we
begin with the structure of section 112(n)(1)(A). As an initial matter,
the order of the terms in the phrase ``appropriate and necessary''
suggests that the first decision EPA must make is whether regulation of
Utility Units under section 112 is ``appropriate.'' Even if EPA
determines that regulation of Utility Units under section 112 is
appropriate, it must still determine whether such regulation is also
necessary. Were EPA to find, however, that regulation of Utility Units
under section 112 met only one prong, then regulating Utility Units
under section 112 would not be authorized by the statute.
The structure of section 112(n)(1)(A) also reveals that the
appropriate and necessary finding is to be made by reference to the
reasonably anticipated public health risks of utility HAP emissions
that remain after ``imposition of the requirements of th[e] Act.'' The
first sentence of section 112(n)(1)(A) contains an important direction
to EPA, which sets the predicate for the entire provision. That first
sentence calls for EPA to identify the hazards to public health
reasonably anticipated to occur as a result of the utility HAP
emissions remaining ``after imposition of the requirements of th[e]
Act.'' Stated differently, Congress wanted EPA to identify the utility
HAP emissions that would remain ``after imposition of the requirements
of th[e] Act'' and identify the hazards to public health reasonably
anticipated to occur as the result of such emissions. As noted above,
we interpret the phrase ``imposition of the requirements of th[e] Act''
to include those CAA requirements that EPA should have reasonably
anticipated would be implemented and would result in reductions of
utility HAP emissions.\18\ Congress' focus on the other requirements of
the CAA reflects its recognition that Utility Units are subject to
numerous CAA provisions and its intent to avoid duplicative and
unnecessary regulation. We therefore reasonably conclude that the
appropriate and necessary finding is to be made by reference to the
reasonably anticipated public health risks from utility HAP emissions
that remain ``after imposition of the requirements of th[e] Act.''
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\18\ The comments of Rep. Oxley, a member of the Conference
Committee, about section 112(n)(1)(A) support EPA's interpretation
of that provision. Rep. Oxley stated:
Pursuant to section 112(n), the Administrator may regulate
fossil fuel fired electric utility steam generating units only if
the studies described in section 112(n) clearly establish that
emissions of any pollutant, or aggregate of pollutants, from such
units cause a significant risk of serious adverse effects on the
public health. Thus, if the Administrator regulates any of these
units, he may regulate only those units that he determines--after
taking into account compliance with all other provisions of the CAA
and any other federal, state or local regulation and voluntary
emission reductions--have been demonstrated to cause a significant
threat of adverse effects on public health.
136 Cong. Rec. H12911, 12934 (daily ed. Oct. 26, 1990)
(Statement of Rep. Oxley) (emphasis added).
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b. EPA's interpretations of the terms ``appropriate'' and
``necessary.'' (i) Appropriate. In December 2000, EPA found that it was
appropriate to regulate coal- and oil-fired Utility Units under section
112. At that time, we did not provide an interpretation of the term
``appropriate.'' Instead, we focused on the following facts and
circumstances. We first found that it was ``appropriate'' to regulate
coal- and oil-fired Utility Units under section 112 because ``mercury
in the environment presents significant hazards to public health.'' See
65 FR 79830. We also determined that it was appropriate to regulate
oil-fired Utility Units based on the uncertainties ``regarding the
extent of the public health impact from HAP emissions from'' such
units. See 65 FR 79830. Finally, we found that it was appropriate to
regulate HAP emissions from coal-and oil-fired units under section 112
because we had identified control options that we anticipated would
effectively reduce certain HAP emissions. We also indicated that
certain control options could ``greatly reduc[e] mercury control
costs.'' See 65 FR 79830.
In January 2004, we proposed reversing our ``appropriate'' finding
in large part. Specifically, we proposed that it is not ``appropriate''
to regulate coal-fired units on the basis of non-Hg HAP and oil-fired
units on the basis of non-Ni HAP because the record that was before the
Agency in December 2000 indicates that emissions of such pollutants do
not result in hazards to public health. See Section IV.B.
Webster's dictionary defines the term ``appropriate'' to mean
``especially suitable or compatible.'' Miriam-Webster's Online
Dictionary, 10th ed. Determining whether something is ``especially
suitable or compatible'' for a particular situation requires
consideration of different factors. In section 112(n)(1)(A), Congress
requires EPA to determine whether it is ``appropriate'' to regulate
Utility Units under section 112. In making this determination, we begin
as we did in December 2000, by assessing the paramount factor, which is
whether the level of utility HAP emissions remaining ``after imposition
of the requirements of th[e] Act'' would result in hazards to public
health. We determine whether the remaining utility HAP emissions cause
hazards to public health by analyzing available health effects data and
assessing, among other things, the uncertainties associated with those
data, the weight of the scientific evidence, and the extent and nature
of the health effects. See Section VI. If the remaining HAP emissions
from Utility Units do not result in hazards to public health, EPA does
not believe that it would be ``especially suitable''--i.e.,
``appropriate''--to regulate such units under section 112. In this
situation, there would be no need to consider any additional factors
under the ``appropriate'' inquiry because the threshold fact critical
to making a finding that it is appropriate to regulate Utility Units
under section 112 would be missing.
Even if the remaining utility HAP emissions cause hazards to public
health, it still may not be appropriate to regulate Utility Units under
section 112 because there may be other relevant factors particular to
the situation that would lead the Agency to conclude that it is not
``especially suitable'' or ``appropriate'' to regulate Utility Units
under section 112. For example, it might not be appropriate to regulate
the utility HAP emissions remaining ``after imposition of the
requirements of th[e] Act,'' if the controls mandated under section
112(d) would be ineffective at eliminating or reducing the identified
hazards to public health. Similarly, it might not be appropriate to
regulate the
[[Page 16001]]
remaining utility HAP emissions under section 112 if the health
benefits expected as the result of such regulation are marginal and the
cost of such regulation is significant and therefore substantially
outweighs the benefits. These examples illustrate that situation-
specific factors, including cost, may affect whether it ``is
appropriate'' to regulate utility HAP emissions under section 112.\19\
(See Section 112(n)(1)(A).)
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\19\ Nothing precludes EPA from considering costs in assessing
whether regulation of Utility Units under section 112 is appropriate
in light of all of the facts and circumstances presented. The DC
Circuit has indicated that regulatory provisions should be read with
a presumption in favor of considering costs: ``It is only where
there is `clear congressional intent to preclude consideration of
cost' that we find agencies barred from considering costs.
[Citations omitted.]'' Michigan v. EPA, 213 F.3d 663, 678 (DC Cir.
2000), cert. den., 532 U.S. 903 (2001) (upholding EPA's
interpretation of ``contribute significantly'' under CAA section
110(a)(2)(D) to include a cost component). The Supreme Court's
decision in Whitman v. American Trucking Assn's (ATA), Inc., 531
U.S. 457 (2001), is not to the contrary. In that case, the Court
held that EPA lacked authority to consider costs in the context of
setting the national ambient air quality standards under CAA section
109(b)(1), because the ``modest words `adequate margin' and
`requisite' ' in that section do not ``leave room'' to consider
cost. 531 U.S. 466. By contrast, EPA is not setting emission
standards in today's action, but rather determining, as Congress
directed, whether it is ``appropriate'' and ``necessary'' to
regulate Utility Units under CAA section 112. The terms
``appropriate'' and ``necessary'' are broad terms, which by contrast
to the terms at issue in ATA do, in fact, leave room for
consideration of costs in deciding whether to regulate utilities
under section 112. Moreover, the legislative history of section
112(n) indicates that Congress intended for EPA to consider costs.
See 136 Cong. Rec. H12911, 12934 (daily ed. Oct. 26, 1990)
(statement of Rep. Oxley) (``[T]he conference committee produced a
utility air toxics provision that will provide ample protection of
the public health while avoiding the imposition of excessive and
unnecessary costs on residential, industrial and commercial
consumers of electricity.''). Finally, section 112(n)(1)(A) requires
EPA to consider alternative control strategies, and the focus on
such strategies may reasonably be read as further evidence of the
relevance of costs. See, e.g., 65 FR 79830 (discussing costs in
relation to certain technologies).
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It cannot be disputed that Congress under section 112(n)(1)(A)
entrusted EPA to exercise judgment by evaluating whether regulation of
Utility Units under section 112 is, in fact, ``appropriate.'' We
believe that in exercising that judgment, we have the discretion to
examine all relevant facts and circumstances, including any special
circumstances that may lead us to determine that regulation of Utility
Units under CAA section 112 is not appropriate.\20\
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\20\ Significantly, in December 2000, we acknowledged that
factors other than the hazards to public health resulting from
utility HAP emissions should be examined in determining whether
regulation of Utility Units is appropriate under section 112.
Indeed, after concluding that the Hg emissions from coal-fired
Utility Units caused hazards to public health, we proceeded with the
appropriate inquiry and examined whether there were any control
technologies that could effectively reduce Hg. We also commented on
the costs of achieving such reductions. See, e.g., 65 FR 79828,
79830.
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(ii) Necessary. Like the ``appropriate'' finding, the ``necessary''
finding must be made by reference to the utility HAP emissions
remaining after imposition of the requirements of the CAA.
Specifically, we interpret the term ``necessary'' in section
112(n)(1)(A) to mean that it is necessary to regulate Utility Units
under section 112 only if there are no other authorities available
under the CAA that would, if implemented, effectively address the
remaining HAP emissions from Utility Units. Assessing whether an
alternative authority would effectively address the remaining utility
HAP emissions would involve not only: (a) An analysis of whether the
alternative legal authority, if implemented, would address the
identified hazards to public health, which was a concept specifically
addressed in December 2000 and in the January 2004 proposal, but also
(b) an analysis of whether the alternative legal authority, if
implemented, would result in effective regulation, including, for
example, its cost-effectiveness and its administrative effectiveness.
See Michigan v. EPA, 213 F.3d, 663, 678 (addressing consideration of
costs).
This interpretation of the term ``necessary'' differs slightly from
the interpretation advanced in December 2000 and January 2004. In
December 2000 and January 2004, we interpreted the term ``necessary''
to mean that it is only necessary to regulate Utility Units under
section 112 if there are no other authorities under the CAA that would
adequately address utility HAP emissions. Several commenters noted that
under this interpretation, EPA could never regulate HAP under section
112 if it identified an alternative viable legal authority. In light of
these comments and further review of section 112(n)(1)(A), we refined
our interpretation of the term ``necessary'' as noted above. We agree
that if we found an alternative authority under the CAA but we also
determined that such authority would not effectively address the
remaining HAP emissions, we should be able to address those emissions
under section 112. Accordingly, we maintain that it is necessary to
regulate Utility Units under section 112 only if there are no other
authorities under the CAA that, if implemented, would effectively
address the remaining HAP emissions from Utility Units.
Some commenters argued that the ``appropriate and necessary''
finding is a public health threshold finding, not an investigation into
whether another provision of the CAA would address HAP emissions from
utilities. This argument is without merit, however, because it
conflates the terms ``appropriate'' and ``necessary'' and renders one
term mere surplusage. Congress required EPA to determine whether it was
both appropriate and necessary to regulate Utility Units under section
112. EPA agrees that it must evaluate the hazards to public health
associated with HAP from utilities in terms of assessing whether
regulation under section 112 is ``appropriate.'' But Congress meant
something different by the term ``necessary,'' and EPA's interpretation
of that term is reasonable. Moreover, we believe that the emissions
inquiry envisioned under the first sentence of section 112(n)(1)(A) is
distinct from the ``necessary'' inquiry called for by the last sentence
of section 112(n)(1)(A), because under the ``necessary'' inquiry the
issue is not whether EPA reasonably anticipated that a particular
provision of the CAA will be implemented and will reduce HAP emissions,
but rather whether there are any other authorities in the CAA that
could be implemented, and if implemented, could effectively address the
hazards to public health that result from the remaining HAP emissions.
Other commenters argued that EPA cannot consider other statutory
authorities under the ``necessary'' prong of the ``appropriate and
necessary'' inquiry because those authorities do not provide for
regulation of utility HAP according to the provisions of CAA section
112(d) and (f). This argument is also without merit because it again
renders mere surplusage the ``necessary'' prong of the determination.
Moreover, as explained above, Congress did not incorporate the
requirements of section 112(f) into section 112(n)(1)(A), but instead,
as we interpret section 112(n)(1)(A), called on EPA to consider the
``hazards to public health reasonably anticipated to occur'' from
utility HAP emissions after imposition of the requirements of the CAA,
in determining whether it is both appropriate and necessary to regulate
Utility Units under section 112.
3. The Timing and Nature of the ``Appropriate and Necessary''
Determination
Congress set no deadline in section 112(n)(1)(A) by which EPA must
determine whether regulation of Utility Units is appropriate and
necessary. We believe that Congress provided
[[Page 16002]]
sufficient discretion under section 112(n)(1)(A)--in terms of both the
substance and the timing of the appropriate and necessary finding--that
nothing precludes us from revising our appropriate and necessary
finding if we determine either that the finding was in error based on
information before the Agency at the time of the finding, or that the
finding is incorrect given new information concerning utility HAP
emissions obtained after issuance of the finding. Both of these
situations are present here, as explained in section IV below.
Moreover, EPA reasonably interprets the last sentence of section
112(n)(1)(A) as authorizing EPA to issue separate appropriate and
necessary findings for different subcategories of ``electric utility
steam generating units.'' EPA typically subcategorizes large source
categories such as utilities. This is especially true for Utility Units
because the nature of the fuel used in different units (e.g., coal-,
oil-, or gas-fired Utility Units), affects the type and amount of HAP
emitted from the units, which, in turn, affects the issue of whether
hazards to public health may exist from such emissions.\21\ Even where
section 112(n)(1)(A) read to require EPA to make only one appropriate
and necessary finding for all ``electric utility steam generating
units,'' EPA's conclusions, as described below, would remain the same.
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\21\ We received no adverse comments concerning our
subcategorization of Utility Units for purposes of section
112(n)(1)(A).
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IV. Revision of the December 2000 Appropriate and Necessary Finding
In Section II above, we summarize the December 2000 appropriate and
necessary finding for coal- and oil-fired Utility Units. In this
section, we explain why we now believe that the December 2000 finding
lacked foundation and therefore was erroneous. We also address below
certain new information obtained since the finding that confirms that
it is not appropriate and necessary to regulate coal- and oil-fired
Utility Units under section 112. Our discussion below is divided into
two sections, the first of which concerns the December 2000 finding for
coal-fired units, and the second of which addresses the December 2000
finding for oil-fired units.
A. Revision of the December 2000 Appropriate and Necessary Finding for
Coal-fired Units
The majority of the December 2000 finding concerned Hg emissions
from coal-fired Utility Units. See, e.g., 65 FR 79826 (``mercury * * *
is emitted from coal-fired units, and * * * is the HAP of greatest
concern to public health from the industry.''); 65 FR 79829-30
(conclusions section of December 2000 finding focuses almost
exclusively on Hg); Utility Study, ES-27 (``mercury from coal-fired
utilities is the HAP of greatest potential concern.''). For that
reason, we first address how EPA erred in making the appropriate and
necessary finding for coal-fired units based on Hg emissions. We then
discuss the December 2000 finding for coal-fired units with regard to
non-Hg HAP.
1. It Is Not Appropriate and Necessary To Regulate Coal-Fired Units on
the Basis of Hg Emissions
a. It Is Not Appropriate to Regulate Coal-fired Units on the Basis
of Hg Emissions. As noted above, EPA's December 2000 ``appropriate''
finding is framed primarily in terms of health effects resulting from
Hg emissions from coal-fired Utility Units.\22\ See 65 FR 79829. The
December 2000 finding also discusses environmental effects, primarily
in the context of public health. In particular, the appropriate finding
discusses the effects of Hg on fish because the public's primary route
of exposure to Hg is through consumption of fish containing
methylmercury. See 65 FR 79829-30. See also Section VI (discussing
health effects of Hg). The December 2000 finding also discusses briefly
the effects of methymercury on certain fish-eating wildlife, such as
racoons and loons. See 65 FR 79830.
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\22\ The ``appropriate'' rationale set forth in the December
2000 finding focused exclusively on Hg with regard to coal-fired
Utility Units. The December 2000 ``necessary'' finding can be read,
however, to suggest that under the appropriate prong, EPA also
determined that non-Hg from coal-fired Utility Units resulted in
hazards to public health. See 65 FR 79830 (``It is necessary to
regulate HAP emissions from coal- and oil-fired'' Utility Units
under section 112 ``because the implementation of other requirements
of the CAA will not address the serious public health and
environmental hazards arising from such emissions.''). As explained
below in section IV.B, the record that was before the Agency in
December 2000 confirms that the non-Hg HAP emissions remaining
``after imposition of the requirements of th[e] Act'' do not result
in hazards to public health. In the proposed rule, EPA solicited
comment on this issue. We did not receive any new information
concerning non-Hg HAP during the comment period that would cause us
to change our position as to these HAP.
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As explained above, EPA interprets section 112(n)(1)(A) as not
requiring the Agency to consider environmental effects of utility HAP
emissions that are unrelated to public health. Nevertheless, EPA
believes it has authority under the ``appropriate'' inquiry to consider
other factors, including non-public health related environmental
factors. As explained above, however, given the focus in section
112(n)(1)(A) on hazards to public health, we believe that environmental
factors unrelated to public health, although they can be considered in
the appropriate inquiry, may not independently or, in conjunction with
one another, justify regulation of Utility Units under section 112 when
EPA has concluded that hazards to public health are not reasonably
anticipated to result from utility HAP emissions.
EPA reasonably addressed non-public health related environmental
factors, such as exposure to wildlife, in the December 2000 finding,
because we separately concluded that Hg emissions from coal-fired
Utility Units pose hazards to public health. As explained below, we
believe that our December 2000 appropriate finding lacks foundation,
and that conclusion is supported by certain recent information.
Specifically, we conclude today that the level of Hg emissions
remaining after imposition of the requirements of the Act will not
cause hazards to public health, and therefore we need not consider
other factors, such as non-public health related environmental effects.
We do, of course, discuss the effects of Hg on fish, because the
ingestion of fish contaminated with methylmercury is the public's
primary route of exposure to Hg. See Section VI (discussing health
effects of Hg).\23\
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\23\ We note, however, that as part of our overall inquiry into
the effects of Hg emissions, we assessed the available information
on the environmental effects of Hg emissions, including effects that
appear to be unrelated to public health. See 1997 Mercury Report to
Congress. While that information, in a very general sense, suggests
that environmental effects of Hg emissions (unrelated to public
health) may be of some concern and therefore warrant further study,
the available information is not specific to the effects of Hg
emissions from domestic utilities. See RIA Appendix C. Thus, even if
EPA were either required or permitted to give unlimited
consideration to these non-health-related environmental effects of
utility Hg emissions in making the regulatory determination under
section 112(n)(1)(A), we would conclude that there is insufficient
causal information to conclusively link utility emissions to
deleterious effects (in wildlife) from Hg exposure.
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As noted above, EPA's December 2000 appropriate finding for coal-
fired units hinged primarily on the health and environmental effects
resulting from Hg emissions. See 65 FR 79830 (``mercury in the
environment presents significant hazards to public health and the
environment.''). This finding lacks foundation, however, for the
reasons described below.
(i) The December 2000 Appropriate Finding Is Overbroad To The
Extent It Hinged On Environmental Effects. EPA should not have made its
appropriate
[[Page 16003]]
finding because of ``hazards to * * * the environment'' resulting from
Hg emissions from coal-fired Utility Units. Section 112(n)(1)(A)
requires EPA to analyze only the ``hazards to public health'' resulting
from utility HAP emissions, not the environmental effects caused by
such emissions. Under section 112(n)(1)(A), the condition precedent for
regulation under section 112 is public health hazards, not
environmental effects, which Congress included in other provisions of
section 112. See, e.g., 112(c)(3) (``a threat of adverse effect to
human health or the environment.''). The Supreme Court has recognized
that ``where Congress includes particular language in one section of a
statute but omits it in another section of the same Act, it is
generally presumed that Congress acts intentionally * * * in the
disparate inclusion or exclusion.'' Russello v. United States, 464 U.S.
16, 23 (1983). Accordingly, EPA erred in its December 2000
``appropriate'' finding to the extent that it hinged on the
environmental effects of HAP, including Hg.
(ii) The December 2000 Appropriate Finding Lacks Foundation Because
EPA Did Not Fully Consider The Hg Reductions That Would Result From
``Imposition of the Requirements of th[e] Act.'' As explained above,
EPA interprets section 112(n)(1)(A) as providing that the
``appropriate'' finding should be made by reference to the level of HAP
emissions remaining after ``imposition of the requirements of th[e]
Act.'' We reasonably interpret the phrase ``imposition of the
requirements of th[e] Act'' to include those requirements that EPA
should have reasonably anticipated would be implemented and would
result in reductions of utility HAP emissions.
The December 2000 ``appropriate'' finding lacks foundation because
EPA failed to fully account for the Hg emissions remaining after
``imposition of the requirements of th[e] Act.'' \24\ That failure
resulted in an overestimate of the remaining utility Hg emissions,
which is the level of emissions that we considered in making our
December 2000 appropriate finding. Had we properly considered the Hg
reductions remaining ``after imposition of the requirements of th[e]
Act'' in December 2000, we might well have (and, as discussed below,
now believe should have) reached a different conclusion as to whether
it was ``appropriate'' to regulate coal-fired units on the basis of Hg
emissions.
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\24\ For ease of reference, we refer to the level of utility Hg
emissions remaining ``after imposition of the requirements'' of the
CAA as the ``remaining Hg emissions.''
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We begin our analysis with a brief background concerning the
Utility Study. In an attempt to address the requirement in section
112(n)(1)(A) of evaluating utility emissions ``after imposition of the
requirements of th[e] Act'', the Utility Study estimates utility HAP
emissions as of the year 2010. See Utility Study ES-1. In quantifying
2010 utility HAP emissions, our analysis focused almost exclusively on
the acid rain provisions of Title IV. Title IV of the CAA establishes a
national, annual emissions cap for sulfur dioxide (SO2)
emissions from Utility Units, which is to be implemented in two phases.
Phase I commences January 1, 1995, and Phase II on January 1, 2000.
EPA relied in the Utility Study on a 1997 Department of Energy
report concerning the effects of the implementation of Title IV of the
CAA on utilities. Utility Study 2-31 to 2-33, 2-39. That report
provides that 53 percent of Utility Units subject to Phase 1
requirements switched to a lower-sulfur coal, 27 percent purchased
additional emissions allowances, and 16 percent (i.e., 27 Utility
Units) installed flue gas scrubbers to comply with the Phase I
requirements.\25\ In the 2010 utility HAP emissions analysis, EPA
accounted for the 27 Utility Units that installed scrubbers to comply
with the phase I requirements. Utility Study 2-31. EPA accounted for
these scrubbers in the 2010 analysis because it recognized that
scrubbers, which control SO2, achieve HAP reductions,
including Hg.\26\ Utility Study at ES-19 & 25, 1-2, 2-32, 3-14
(discussing ability of PM controls (including SO2 controls)
to reduce Hg and other HAP emissions from Utility Units).\27\
Significantly, however, EPA did not incorporate into the 2010 utility
HAP emissions analysis the Hg reductions that we reasonably should have
anticipated achieving through implementation of the requirements of
Title I of the CAA. See Utility Study, at 2-31 to 2-33. In this regard,
EPA erred in, at least, two respects.
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\25\ Flue gas scrubbers are a type of control technology used to
control SO2.
\26\ EPA did not account in its 2010 analysis for the
installation of any scrubbers associated with Phase II of the acid
rain program, because it only had industry projections as to which
units would install scrubbers and, for various reasons, it did not
find those projections reliable. Utility Study 2-31 to 2-33.
\27\ In the December 2000 finding, we indicate that recent data
show that technologies used to control criteria pollutants, like PM,
SO2, and NOX are not ``effective'' in
controlling Hg. See 65 FR 79828. This statement is incorrect. It is
not only inconsistent with other statements in the December 2000
finding, it is contrary to the record that was before the Agency in
December 2000. The record indicates that technologies used to
control PM, SO2, and NOX do reduce HAP,
including Hg. Furthermore, insofar as Hg is concerned, these
technologies result in important reductions of oxidized Hg, which is
the type of Hg that tends to deposit locally and regionally. Utility
Study at ES-19 & 25, 1-2, 2-32, 3-14.
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First, EPA erred by not accounting for the utility Hg reductions
that it should have reasonably anticipated would result from
implementation of the nonattainment provisions of Title I, including,
in particular, the revised NAAQS for ozone that EPA issued in July
1997, before the report was completed, under the nonattainment
provisions.\28\ The Utility Study expressly recognizes that the revised
NAAQS would result in, among other things, significant reductions of
SO2 and NOX. See generally Utility Study at 1-2
to 1-3. The Utility Study also indicates that the revised NAAQS would
result in approximately a 16 percent reduction (11 tons per year) of Hg
emissions by 2010, primarily due to the fact that Utility Units would
need to install controls, like scrubbers, to meet the SO2
reductions needed to attain the PM NAAQS. (Utility Study 1-3, ES-25, 3-
14). Notwithstanding these significant estimated reductions, EPA did
not take these reductions into account in its 2010 utility HAP
emissions analysis.\29\ ES-25 (``analyses performed to assess
compliance with the revised NAAQS * * * indicate that Hg emissions in
2010 may be reduced by approximately 16 percent (11 tpy) over those
projected in this report.''). Accordingly, the December 2000
appropriate finding lacks foundation because we made the finding based
on an inaccurate level of Hg emissions remaining after imposition of
the requirements of the CAA. Had we properly accounted in December 2000
for the 11 tons per year of Hg reductions that we projected in our own
analyses, we might well have (and, as discussed below, now believe
should have) concluded that it was not appropriate to regulate coal-
fired units under section
[[Page 16004]]
112 on the basis of the remaining Hg emissions. Indeed, recent modeling
confirms that we likely would have reached such a conclusion. That
modeling specifically demonstrates that about a 13 ton reduction in
utility Hg emissions from 1990 levels would result in a level of Hg
emissions that does not cause hazards to public health. We conducted
these recent analyses in conjunction with the recently signed Clean Air
Interstate Rule (``CAIR'') issued pursuant to CAA section 110(a)(2)(D),
which is explained more fully in section V below.
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\28\ For additional background concerning the nonattainment
provisions of Title I and the revised PM and ozone NAAQS, see
Section V below.
\29\ In the Utility Study, we explained that we did not account
for the identified Hg reductions in the 2010 analysis because we
lacked information on the specific number of units that would
install scrubbers and related PM control technologies since we had
not yet designated which areas of the country were in nonattainment
of the revised NAAQS. See Utility Study 2-32. Although we had not
yet designated areas of the country as being in nonattainment of the
revised standards, as explained in section V, we were generally
aware of the likelihood of widespread nonattainment with the revised
NAAQS. In fact, that recognition formed the basis of our analysis
that resulted in an estimated 16 percent reduction in Hg emissions
from implementation of the revised NAAQS.
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Second, EPA erred in December 2000 by not examining, and therefore
not accounting for, the reductions in utility Hg emissions that would
result from two other rules issued pursuant to Title I of the CAA. The
first rule set new source performance standards (``NSPS'') under CAA
section 111(b) for NOX emitted from utility and industrial
boilers. The second rule, promulgated under CAA section 110(a)(2)(D),
requires 22 states and the District of Columbia to revise their state
implementation plans (``SIP'') to mitigate for the interstate transport
of ozone. This rule is called the NOX SIP-call rule and
requires significant reductions of NOX emissions in the
eastern half of the United States. EPA determined those NOX
reductions by analyzing Utility Units and large nonpoint utility
sources and identifying the amount of reductions that those units could
achieve in a ``highly cost-effective'' manner. Both the NOX
SIP call and the NSPS rule were premised on a NOX control
technology called selective catalytic reduction (``SCR''). The data on
the effectiveness of SCR at controlling utility Hg emissions was
limited in February 1998. See Utility Study 2-32. As of December 2000,
however, EPA had additional data that confirmed that SCR would lead to
certain reductions in utility Hg emissions. See, e.g., 65 FR 79829
(SCR--a NOX control technology ``may also oxidize mercury
and therefore enhance mercury control.''). EPA therefore should have
been able to reasonably estimate in December 2000 that some Hg
reductions would occur as the result of implementation of the NSPS and
the NOX SIP-call rules. Because we did not account for
reductions in utility Hg emissions as the result of implementation of
these rules, we made our appropriate finding in December 2000 based on
an incorrect estimate of the remaining Hg utility emissions. Based on
all of the above, the December 2000 ``appropriate'' finding lacked
foundation because it was not based on the level of utility Hg
emissions remaining ``after imposition of the requirements of th[e]
Act.''
(iii) It Is Not Appropriate to Regulate Coal-fired Utility Units
Under Section 112 on the Basis of Hg Emissions Because New Information
Reveals that the Level of Utility Hg Emissions Remaining After
Imposition of the Requirements of the CAA Does Not Cause Hazards to
Public Health. In addition to the errors noted above with regard to the
December 2000 finding, we have new information that confirms that it is
not appropriate to regulate coal-fired units under section 112 on the
basis of Hg emissions. EPA recently signed a rulemaking implementing
section 110(a)(2)(D), called the Clean Air Interstate Rule. (See
Section V below for further discussion of CAIR.) This rulemaking, among
other things, requires a number of eastern states to develop SIPs
providing for substantial reductions of SO2 and
NOX emissions. Although affected states retain flexibility
to decide how to achieve those reductions, EPA has concluded that the
reductions from Utility Units are highly cost-effective, and
anticipates that affected states will meet their emission reduction
obligations by controlling Utility Unit emissions. EPA also concluded
that the technologies that most cost-effectively achieve SO2
and NOX reductions for Utility Units are scrubbers for
SO2 and SCR for NOX. These technologies, as noted
above, result in reductions of utility Hg emissions. In conjunction
with the CAIR rulemaking, EPA analyzed the nature of Hg emissions that
would remain after implementation of the rule and assumed that states
would choose to regulate Utility Units, which is the most cost-
effective option for achieving the required reductions. That modeling
reveals that the implementation of section 110(a)(2)(D), through CAIR,
would result in a level of Hg emissions from Utility Units that would
not cause hazards to public health. See Section V for further detail.
Because this new information demonstrates that the level of Hg
emissions projected to remain ``after imposition of'' section
110(a)(2)(D) does not cause hazards to public health, we conclude that
it is not appropriate to regulate coal-fired Utility Units under
section 112 on the basis of Hg emissions.\30\
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\30\ The reductions achieved through CAIR overlap, in part, with
the 11 tons per year of reductions discussed in the prior section,
which EPA estimated in 1998 would occur as the result of
implementation of the revised NAAQS. The reductions necessarily
overlap because in the Utility Study EPA projected forward 13 years,
by examining utility HAP emissions in 2010. In analyzing the level
of utility Hg emissions remaining ``after imposition of [section
110(a)(2)(D)]'' through CAIR, we are accounting for the full impact
of CAIR and that necessarily includes reductions that occur between
today and 2010, and beyond. See Section V (discussing requirements
of CAIR in 2010 and 2015).
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In addition to CAIR, we today finalized a rule pursuant to section
111, called the Clean Air Mercury Rule (``CAMR''). (See section VII
below for further discussion of CAMR.) That rule requires even greater
reductions in Hg emissions from coal-fired Utility Units than CAIR. As
explained in greater detail in Section VI, the computer modeling
completed in support of that rule, like the modeling completed on CAIR,
demonstrates that CAMR, independent of CAIR, will result in levels of
utility Hg emissions that do not result in hazards to public health.
Thus, the implementation of CAMR provides an independent basis for our
conclusion that it is not appropriate to regulate coal-fired Utility
Units under section 112 because the utility Hg emissions remaining
after implementation of section 111 will be at a level that results in
no hazards to public health.\31\
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\31\ Nothing in section 112(n)(1)(A) precludes EPA from revising
a prior appropriate and necessary finding based on new information.
In light of CAIR and, independently, CAMR, we can now reasonably
anticipate the reductions in utility Hg emissions that would result
from implementation of sections 110(a)(2)(D) and 111 of the CAA.
Accordingly, we are accounting for those reductions in assessing the
level of utility Hg emissions remaining after ``imposition of the
requirements of th[e] Act,'' which include section 110(a)(2)(D) and
111. We then based our new appropriate finding on these remaining Hg
emissions.
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b. It Is Not Necessary to Regulate Coal-fired Units on the Basis of
Hg Emissions. Even if Congress had intended EPA to focus on a more
limited set of requirements in interpreting the phrase ``after
imposition of the requirements of th[e] Act,'' that would mean only
that EPA did not err in December 2000 in terms of its ``appropriate''
finding for coal-fired units based on Hg emissions. EPA nevertheless
concludes today that it still erred in December 2000 with regard to its
``necessary'' finding. In section 112(n)(1)(A), Congress called on EPA
to make a finding as to whether regulation of Utility Units under
section 112 was not only ``appropriate,'' but ``necessary.'' To give
effect to the term ``necessary,'' we interpret the ``necessary'' prong
of the section 112(n)(1)(A) inquiry to require EPA to examine whether
there are any other available authorities under the CAA that, if
implemented, would effectively address the remaining Hg emissions from
coal-fired Utility Units.
[[Page 16005]]
In December 2000, EPA did not consider CAA sections 110(a)(2)(D)
\32\ and 111,\33\ which are viable alternative authorities under the
CAA, that, if implemented, would effectively address the remaining
utility Hg emissions. See Section VI below. Regulation under these
authorities would effectively address the remaining utility Hg
emissions for two primary reasons. First, as demonstrated in section VI
below, the level of utility Hg emissions remaining after implementation
of CAIR will not result in hazards to public health. Similarly, as
shown in section VI below, the CAMR, which requires even greater Hg
reductions than CAIR, will, once implemented, result in a level of
utility Hg emissions that does not cause hazards to public health.
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\32\ In January 2004, the proposed section 111 rule was
premised, in part, on the reductions in Hg emissions that EPA
anticipated would be achieved through CAIR. In response to comments
received on the CAMR, we conducted additional modeling that
confirmed that CAIR alone, once implemented, would result in levels
of utility Hg emissions that do not cause hazards to public health.
(See Section VI below). Accordingly, we now believe that CAA section
110()(2)(D) constitutes yet another viable authority under the CAA
that, once implemented, will effectively address the remaining
utility Hg emissions.
\33\ In the Utility Study, we considered section 111 of the CAA,
noting that ``new source performance standards currently provide the
major regulatory authority for the control of air emissions from
utilities.'' Utility Study 1-6. We recognized that we had issued
NSPS for PM for Utility Units and we noted that such requirements
would result indirectly in the control of certain HAP, including Hg.
EPA did not, however, address in the Utility Study the question of
whether HAP from utilities could be regulated under the authority of
section 111 [Utility Study 1-5-6]. As explained in the proposed
rule, we conducted a thorough re-evaluation of the provisions of the
CAA and have concluded that section 111 provides authority to
regulate HAP from new and existing Utility Units. See Section VII
below (discussing legal authority under section 111).
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In addition, controlling Hg emissions through a cap-and-trade
system--whether that control is through direct regulation under section
111 or indirect regulation under section 110(a)(2)(D)--is an efficient
means of regulating Utility Units. See CAMR final rule (signed on March
15, 2005) (discussing basis and purpose of the regulations). As an
initial matter, a cap-and-trade system, as opposed to the control
regime imposed pursuant to section 112(d), provides Utility Units the
flexibility to pursue a least-cost compliance option to achieve the
required emissions reductions.
Sources have the choice of complying with the reductions in a
variety of ways, such as fuel switching, installing different pollution
control technologies, installing new or emerging control technologies
and/or buying allowances to emit from another source that has
controlled its emissions to a level below what the regulation requires.
This compliance flexibility allows Utility Units to respond to changing
electricity generation demands, economic market conditions or
unanticipated weather situations (e.g., extremely hot or cold periods)
without jeopardizing their compliance status, or the stability of the
overall cap. In addition, the certainty provided by the emissions cap
and the timeline for declining emissions provide important information
for industry to make strategic, long-range business decisions.
Moreover, under a cap-and-trade approach, most of the reductions
are projected to result from larger units installing controls and
selling excess allowances, due to economies of scale realized on the
larger units versus the smaller units. Indeed, EPA's modeling of
trading programs demonstrates that large coal-fired Utility Units,
which tend to have higher levels of Hg emissions, will achieve the most
cost-effective emission reductions. These units are more likely to
over-control their emissions and sell allowances, than to not control
and purchase allowances. This model prediction is consistent with
principles of capital investment in the utility industry. Under a
trading system where the firm's access to capital is limited, where the
up-front capital costs of control equipment are significant, and where
emission-removal effectiveness (measured in percentage of removal) is
unrelated to plant size, from an economics standpoint, the utility
company is more likely to allocate pollution-prevention capital to its
larger facilities than to the smaller plants (since more allowances
will be earned from the larger facilities). Economies of scale of
pollution control investment will also favor investment at the larger
plants. Further, insofar as large coal-fired Utility Units tend to be
newer and/or better maintained than medium-sized and small facilities,
it can be expected that companies will favor investments in plants with
a longer expected lifetime. These modeled predictions are consistent
with the pattern of behavior that EPA has observed over the past decade
through implementation of the SO2 emissions trading program
under Title IV of the CAA. Thus, under a cap-and-trade program, Hg
reductions result from units that are most cost effective to control,
which enables those units that are not considered to have cost
effective control alternatives to use other mechanisms for compliance,
such as buying allowances. By contrast, regulating pursuant to a
control regime like section 112(d) does not result in the cost
efficiencies that are attendant a cap-and-trade program. For example,
under section 112(d), each facility must meet a specific level of
emission control, which can result in increased compliance costs,
particularly for the smaller Utility Units given economies of scale.
Finally, trading provides greater incentives for the development
and adoption of new technologies, which could lead to a greater level
of emissions control. See generally 69 FR 4686-87. An additional
benefit of the cap-and-trade programs under sections 110(a)(2)(D) and
111 is that they dovetail well with each other. In particular, the
coordinated regulation of SO2, NOX, and Hg
through CAIR and CAMR improves the cost effective manner of regulation
because the reductions are being achieved simultaneously using in some
cases the same technology to control more than one pollutant. In
addition, the cap-and-trade programs under sections 110(a)(2)(D)
complement other cap-and-trade programs that directly affect Utility
Units, such as the NOX SIP-call final rule and the
regulations implementing Title IV, which only further enhances the
efficiencies of emission control from such units.
In light of CAA sections 110(a)(2)(D) and 111, we believe that we
should not have concluded in December 2000 that it ``is necessary'' to
regulate Utility Units under section 112 and therefore our
``necessary'' finding was in error. Moreover, even setting aside the
error that we made in December 2000, we now recognize the availability
of these other statutory provisions and we further conclude today that
it is not necessary to regulate coal-fired Utility Units under section
112 on the basis of the remaining Hg emissions. CAA section
110(a)(2)(D), as implemented through CAIR, and independently section
111, as implemented through CAMR, will effectively address the Hg
emissions remaining from coal-fired Utility Units ``after imposition of
the requirements of th[e] Act.''
In sections V and VII below, we address sections 110(a)(2)(D) and
111 and provide a thorough discussion of the legal authority under each
provision. We also explain in Section VI that after implementation of
CAIR, and independently, CAMR, we do not anticipate hazards to public
health resulting from Hg emissions from coal-fired Utility Units.
[[Page 16006]]
2. It Is Not Appropriate and Necessary to Regulate Coal-Fired Units on
the Basis of Non-Hg Emissions
In the study required by section 112(n)(1)(A), and detailed in the
Utility Study, EPA identified 67 HAP as potentially being emitted by
Utility Units. (Utility Study, ES-4). Based on a screening assessment
designed to prioritize HAP for further evaluation, EPA identified 14
HAP as a priority for further evaluation. (Id.). Of the 14 HAP
identified for further evaluation, 12 HAP (arsenic, beryllium, cadmium,
chromium, manganese, nickel, hydrogen chloride, hydrogen fluoride,
acrolein, dioxins, formaldehyde and radionuclides) were identified for
further study based on potential for inhalation exposure and risks.
(Utility Study, ES-6). Four of those 12 HAP (arsenic, cadmium, dioxins
and radionuclides) plus Hg and lead were considered priority for
multipathway exposure. (Id.). Of those six HAP, four (arsenic, Hg,
dioxins and radionuclides) were identified as the highest priority to
assess for multipathway exposure and risks. (Utility Study, ES-6, 7).
The other 53 HAP were not evaluated beyond the screening assessment.
(Utility Study, ES-7).
In evaluating the potential for inhalation exposure and risks for
the 12 HAP identified through the screening assessment as priority for
that purpose, EPA estimated the high-end inhalation cancer risk for
each HAP identified as a carcinogen and the high-end inhalation
noncancer risks for the remaining HAP for both coal- and oil-fired
Utility Units in 2010. (Utility Study, 6-16, tables 6-8 and 6-9). That
evaluation indicated that there was no maximum individual risk (MIR)
for cancer greater than 1 x 10\-6\ for beryllium, cadmium, dioxin and
nickel emissions from coal-fired Utility Units and for beryllium,
cadmium and dioxin emissions from oil-fired Utility Units. (Id.) With
regard to dioxins, the Utility Study specifically concluded that the
quantitative exposure and risk results did not conclusively demonstrate
the existence of health risks of concern associated with inhalation
exposures to utility emissions on a national scale or from any actual
individual utility. (Utility Study, 11-5). The Utility Study thus
indicates that inhalation of beryllium, cadmium and dioxin emissions
from coal and oil-fired Utility Units and emissions of nickel from oil-
fired Utility Units are not of significant concern from a public health
standpoint because such exposure does not present a maximum individual
risk (MIR) for cancer greater than 1 x 10\-6\. With regard to lead
emissions, EPA found that emission quantities and inhalation risks were
relatively low and, therefore, decided not to conduct future
evaluations of multipathway exposures to lead resulting from Utility
Unit emissions. (Utility Study, ES-24). For arsenic, EPA concluded that
there were several uncertainties associated with both the cancer risk
estimates and the health effects data such that further analyses were
needed to characterize the inhalation risks posed by arsenic emissions
from Utility Units. (Utility Study, ES-21). The inhalation exposure
assessment did not identify any exceedances of the health benchmarks
(e.g., RfCs) for hydrogen chloride or hydrogen fluoride, thus
indicating that Utility Unit emissions of those HAP did not pose a
significant public health concern. (Utility Study chapters 6 and 9.)
a. It Is Not Appropriate to Regulate Coal-fired Units on the Basis
of Non-mercury HAP Emissions. The EPA erred in the December 2000
Regulatory Determination to the extent that its ``appropriate'' finding
for coal-fired Utility Units was based, in any way, on hazards to
public health or the environment arising from emissions of non-mercury
HAP from coal-fired Utility Units. Based on the information before it
at the time, EPA could not have reasonably concluded that coal-fired
Utility Unit non-mercury HAP emissions presented a hazard to public
health. In addition, as stated above, EPA should not have considered
environmental effects in the December 2000 Regulatory Determination's
consideration of whether it was appropriate to regulate HAP emissions
from coal-fired Utility Units under section 112.
(i) Non-Mercury Metallic HAP. In the December 2000 Regulatory
Determination, EPA indicated that there were a few metallic HAP (e.g.,
chromium and cadmium) which were of potential concern for carcinogenic
effects, but stated that ``the results of the risk assessment
(performed in conjunction with the Utility Study) indicate that cancer
risks are not high''. (See 65 FR 79825, 79827.) The EPA acknowledged,
however, that the cancer risks were not low enough to eliminate those
metals as a potential concern for public health (Id.). This latter
statement, at least as it pertains to cadmium, is at odds with the
results of the risk assessment set forth in the Utility Study and
discussed above. In the Utility Study, EPA determined that there was no
maximum individual risk (MIR) for cancer greater than 1 x 10\-6\ due to
inhalation of cadmium emissions from Utility Units. In the Proposed
Rule, EPA stated that although it recognized the existence of
uncertainties with regard to the data and information obtained prior to
the December 2000 Regulatory Determination regarding potential hazards
to public health resulting from Utility Unit emissions of non-mercury
metallic HAP, the Agency believed that the uncertainties associated
with those emissions were so great that it was not appropriate to
regulate them at that time because they do not pose a hazard to public
health that warrants regulation. (69 FR 4652, 4688, January 30, 2004).
The EPA continues to believe that had it properly accounted for the
uncertainties regarding the data and information on potential hazards
to public health resulting from Utility Unit emissions of non-mercury
metallic HAP in making the December 2000 appropriate finding it would
have concluded that it was not appropriate to regulate such emissions
because they do not cause a hazard to public health. The EPA has not
discovered any new information on hazards to public health arising from
such emissions that invalidates this conclusion, either through its own
efforts or in response to the Proposed Rule.
(ii) Dioxins. In the December 2000 Regulatory Determination, EPA
also identified dioxins as being of potential concern and indicated
that they may be evaluated further during the regulatory development
process. (See 65 FR 79825, 79827.) The EPA did not, however, indicate
that those concerns rose to a level that warranted regulation of
dioxins. Thus, EPA did not conclude, and could not have concluded,
based on the record before it at the time of the December 2000
Regulatory Determination that it was appropriate to regulate coal-fired
Utility Unit HAP emissions under section 112 of the CAA on the basis of
dioxin emissions. In the Proposed Rule EPA stated that while it
intended to continue to study dioxins in the future, the Utility Study
and the information EPA had obtained since finalizing the Utility Study
revealed no public health hazards reasonably anticipated to occur as a
result of emissions of dioxins by Utility Units. (See 69 FR 4652,
4688). As is the case with non-mercury metallic HAP, EPA has neither
discovered information on hazards to public health arising from Utility
Unit emissions of dioxins based on its own efforts, nor received such
information in response to the Proposed Rule. The EPA therefore
concludes that its appropriate finding in December 2000 lacked
foundation because it could not have reasonably concluded that the
[[Page 16007]]
level of remaining utility dioxin emissions results in hazards to
public health.
(iii) Acid Gases. In the December 2000 Regulatory Determination,
EPA identified emissions of hydrogen chloride and hydrogen fluoride as
being of potential concern and indicated that such emissions may be
evaluated further during the regulatory development process. (See 65 FR
79825, 79827.) The EPA did not, however, indicate that it believed that
it was appropriate to regulate such emissions, under section 112 or
otherwise. As indicated in the Proposed Rule, EPA did in fact further
evaluate Utility Unit emissions of hydrogen chloride and hydrogen
fluoride. (See 69 FR 4652, 4688, fn. 10; ``Modeling results for
hydrogen chloride, hydrogen fluoride and chlorine emissions from coal-
fired utility boilers'', December 12, 2003, OAR-2002-0056-0015). That
modeling indicates that individuals are not exposed to acid gas
emissions from Utility Units at concentrations which pose hazards to
public health. EPA has neither discovered information on hazards to
public health arising from Utility Unit emissions of acid gases based
on its own efforts, nor received such information in response to the
Proposed Rule. EPA therefore concludes that its appropriate finding in
December 2000 lacked foundation because the level of remaining utility
acid gas emissions does not result in hazards to public health.
For the reasons stated above, EPA finds that it could not
reasonably have concluded that it was appropriate to regulate coal-
fired Utility Units under section 112 due to emissions of non-mercury
HAP based on the record before it at the time of the December 2000
Regulatory Determination. The EPA further finds that it has not itself
discovered any information which would support the conclusion that it
is appropriate to regulate non-mercury HAP emissions by coal-fired
Utility Units under section 112 subsequent to the December 2000
Regulatory Determination, nor has it received any such information in
response to the January 2004 Proposed Rule, the March 2004 Supplemental
Notice or the December 2004 Notice of Data Availability. Further, EPA
has concluded that it did not, and should not, rely on potential
environmental effects alone in determining whether it was appropriate
to regulate coal-fired Utility Units under section 112. The EPA,
therefore, finds that, based on the record before it at the time, it
was in error in determining that it was appropriate to regulate coal-
fired Utility Unit HAP emissions under section 112 to the extent that
the determination was based in any way on the hazards to public health
of non-mercury HAP emissions or on environmental effects resulting from
such emissions.
b. It Is Not Necessary to Regulate Coal-fired Units on the Basis of
Non-Mercury HAP Emissions. In determining whether it is appropriate and
necessary to regulate Utility Unit HAP emissions under section 112, the
threshold question is whether it is appropriate to regulate such
emissions at all. Where, as here, EPA cannot reasonably conclude that
it is appropriate to regulate such emissions, the Agency does not need
to resolve the question of whether it is necessary to regulate such
emissions under section 112, or elsewhere. In any event, even if EPA
could have reasonably concluded that it was appropriate to regulate
non-mercury HAP emissions from coal-fired Utility Units, it would not
have been reasonable for the Agency to find that it was necessary to
regulate such emissions under section 112 since, as discussed above, it
should have realized that there was an available alternative mechanism,
such as section 111, for regulating such emissions had it been
appropriate to do so. See also Section VII below.
B. Revision of the December 2000 Appropriate and Necessary Finding for
Oil-fired Units
1. It Is Not Appropriate and Necessary To Regulate Oil-Fired Units on
the Basis of Nickel Emission
a. It Is Not Appropriate to Regulate Oil-fired Units on the Basis
of Nickel Emissions. In finding that the regulation of HAP emissions
from oil-fired Utility Units was appropriate and necessary in its
December 2000 Regulatory Determination, EPA did not clearly identify
the basis for this finding beyond stating that there remained
uncertainties regarding the extent of the public health impact from HAP
emissions from oil-fired units and that those uncertainties led the
Administrator to find that regulation of HAP emission from such units
under section 112 is appropriate and necessary. (See 65 FR 79825,
79830). Table 1 in the 2000 determination does, however, indicate that
nickel is the metallic HAP emitted in the largest quantities by oil-
fired Utility Units and that some nickel compounds are carcinogenic.
(See 65 FR 79825, 79828). It therefore appears that EPA's finding was
based at least in part on its concerns regarding perceived hazards to
public health arising from inhalation exposure to nickel emissions from
oil-fired Utility Units. This is consistent with the Utility Study
which, based on very conservative assumptions regarding the
carcinogenicity of the nickel emitted by such units, identifies nickel
as the HAP emitted by oil-fired Utility Units which poses the highest
cancer maximum individual risk. (Utility Study, Table 6-3, p. 6-8). The
Utility Study identifies 11 oil-fired utility plants as having
emissions causing maximum individual risk of cancer greater than
10-6 based on nickel emissions (Id.)
In the Proposed Rule, EPA stated that it continued to believe that
the record supports a distinction between the treatment of nickel
emissions from oil-fired Utility Units and other non-nickel HAP
emissions from such units. EPA proposed to conclude that it was not
appropriate to regulate the non-Ni HAP. EPA also proposed to treat
nickel from oil-fired units differently based on the amount of nickel
emitted annually and the scope of adverse health effects (See 69 FR
4652, 4688). Based on its analysis of new information obtained in
response to the Proposed Rule, EPA has determined that the distinction
between nickel and the remaining HAP from oil-fired units cannot be
supported. EPA finds that it is not appropriate to regulate nickel
emissions from oil-fired Utility Units and that it is, therefore, not
appropriate to regulate oil-fired Utility Units. This finding is based
on the following: (1) The significant reductions in the total
nationwide inventory of oil-fired Utility Units; and (2) the changing
fuel mixtures being used at the remaining units.
Nickel emissions from oil-fired Utility Units have been
substantially reduced since the 1998 Utility Report to Congress through
a combination of unit closures and fuel switching. The 11 oil-fired
plants identified in the Utility Study as having emissions causing a
maximum individual risk of cancer greater than 10-6 based on
nickel emissions were comprised of 42 individual units. Of those 42
units, 12 units have permanently ceased operation or are out of
service. (OAR-2002-0056-2046 at pp. 12-13; OAR-2002-0056-5998). In
addition, 6 of the original 42 units have reported to the U.S.
Department of Energy (DOE) that their fuel mix now includes natural
gas. Earlier reports did not show these units as using natural gas as a
fuel. (OAR-2002-0056-5998). The use of natural gas as a part of their
fuel mix would decrease the nickel emissions from these 6 units.
Similarly, another 5 units report using a mix of natural gas and
distillate oil (rather than residual oil) in
[[Page 16008]]
2003. (OAR-2002-0056-5998). Since distillate oil contains less nickel
than the residual oil previously burned by these units, it is
reasonable to assume that these units currently emit less nickel than
was previously the case. Another 2 units now fire a residual oil/
natural gas mixture and have limited their residual oil use through
permit restrictions to no greater than 10 percent of the fuel
consumption between April 1 and November 15, with natural gas being
used for at least 90 percent of total fuel consumption. (OAR-2002-0056-
2046 at p. 13). Finally, five units have effectively eliminated their
nickel emissions since the Utility Study by switching to burning
natural gas exclusively. (OAR-2002-0056-2046 at pp. 12-13; OAR-2002-
0056-5998). Taken as a whole, these changes mean that 30 of the
original 42 units identified in the Utility Study have taken steps to
reduce or actually eliminate their nickel emissions. Of the original 11
plants identified in the Utility Study, only 2, both in Hawaii, have
units for which actions that will result in reduced nickel emissions do
not appear to have been taken. (OAR-2002-0056-6871) In addition to the
closure of the 12 units identified as being of potential concern in the
Utility Study, there has been a steady decrease in the number of oil-
fired Utility Units generally over the past decade and this trend is
likely to continue. In fact, the latest DOE/EIA projections (OAR-2002-
0056-5999) estimate no new utility oil-fired generating capacity and
decreasing existing oil-fired generating capacity through 2025, with an
additional 29.2 gigawatts of combined oil- and natural gas-fired
existing capacity being retired by 2025.
Based on the foregoing, EPA concludes that it is not appropriate to
regulate oil-fired Utility Units under section 112 because we do not
anticipate that the remaining level of utility nickel emissions will
result in hazards to public health.
b. It Is Not Necessary to Regulate Oil-fired Units on the Basis of
Nickel Emissions. Because EPA could not have reasonably found that it
was appropriate to regulate nickel emissions from oil-fired Utility
Units based on the record before it at the time of the December 2000
Regulatory Determination, it should not have made a finding that it was
necessary to regulate such emissions. Information obtained in the
course of the rulemaking since the Proposed Rule has confirmed this
conclusion. In any event, even if EPA could have reasonably concluded
that it was appropriate to regulate nickel emissions from oil-fired
Utility Units, it would not have been reasonable for the Agency to find
that it was necessary to regulate such emissions under section 112
since, as discussed above, it should have realized that there was an
available alternative mechanism, section 111, for regulating such
emissions had it been appropriate to do so. See also Section VII below.
2. It Is Not Appropriate and Necessary To Regulate Oil-Fired Units on
the Basis of Non-Nickel HAP Emissions
a. It Is Not Appropriate to Regulate Oil-fired Units on the Basis
of Non-nickel HAP Emissions. As is the case with emissions of nickel,
the record before EPA at the time of the December 2000 Regulatory
Determination does not reasonably support a finding that it is
appropriate to regulate emissions of any other HAP from oil-fired
Utility Units. In the December 2000 Regulatory Determination, EPA
stated that there remain uncertainties regarding the extent of the
public health impact from HAP emissions from oil-fired Utility Units
and, on that basis, found that it was appropriate and necessary to
regulate oil-fired Utility Units under section 112. (See 65 FR 79825,
79830.) The EPA neither identified the HAP concerning which there were
uncertainties nor identified what those uncertainties were. EPA has
neither discovered information on hazards to public health arising from
the remaining non-nickel emissions of oil-fired Utility Units, nor
received such information in response to the Proposed Rule. EPA
therefore concludes that its appropriate finding in December 2000
lacked foundation because, given the level of remaining non-nickel HAP
emissions from Utility Units, the Agency did not and does not have any
information on the hazards to public health reasonably anticipated to
occur. Indeed, the uncertainties that exist with regard to the data and
information on these emissions are so great that the Agency has not
identified any hazards to public health.
b. It Is Not Necessary to Regulate Oil-fired Units on the Basis of
Non-nickel HAP Emissions. Because EPA finds that it is not appropriate
to regulate oil-fired Utility Units on the basis of non-nickel HAP
emissions, it also finds that it is not necessary to regulate oil-fired
Utility Units on the basis of such emissions. In any event, even if EPA
could have reasonably concluded that it was appropriate to regulate
non-nickel HAP emissions from oil-fired Utility Units, it would not
have been reasonable for the Agency to find that it was necessary to
regulate such emissions under section 112 since, as discussed above, it
should have realized that there was an available alternative mechanism,
section 111, for regulating such emissions had it been appropriate to
do so. See also Section VII below.
V. Statutory and Regulatory Overview of CAA Section 110(a)(2)(D) and
Summary of EPA's Clean Air Interstate Rule, Which Implements Section
110(a)(2)(D)
A. The Clean Air Interstate Rule and Clean Air Act Section 110(a)(2)(D)
1. Background for Promulgation of the Clean Air Interstate Rule
The Administrator signed the notice of final rulemaking for the
Clean Air Interstate Rule (CAIR) on March 10, 2005. The background for
CAIR is fully described in the preambles to the final rule, the notice
of proposed rulemaking, 69 FR 4565 (January 30, 2004) and the notice of
supplemental rulemaking, 69 FR 12398 (March 16, 2004), and is briefly
summarized below.
a. PM 2.5 NAAQS, 8-hour Ozone NAAQS, and the Nonattainment
Problems. By notice dated July 18, 1997, we revised the NAAQS for
particulate matter to add new standards for fine particles, using as
the indicator particles with aerodynamic diameters smaller than a
nominal 2.5 micrometers, termed PM 2.5. 62 FR 38652. We established
health- and welfare-based (primary and secondary) annual and 24-hour
standards for PM 2.5. The annual standard is 15 micrograms per cubic
meter, based on the 3-year average of annual mean PM 2.5
concentrations. The 24-hour standard is a level of 65 micrograms per
cubic meter, based on the 3-year average of the annual 98th percentile
of 24-hour concentrations.
By a separate notice dated July 18, 1997, EPA also promulgated a
revised primary NAAQS for ozone (and an identical secondary ozone
NAAQS). This revised NAAQS, termed the 8-hour NAAQS, specified that the
3-year average of the fourth highest daily maximum 8-hour average ozone
concentration could not exceed 0.08 ppm. (See 40 CFR 50.10) In general,
the revised 8-hour standard is more protective of public health and the
environment and more stringent than the pre-existing 1-hour ozone
standard. Following promulgation of the 8-hour ozone and the PM 2.5
NAAQS, EPA anticipated that many areas of the country, particularly in
the eastern half of the country, would have air quality violating one
or both of those NAAQS.\34\
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\34\ Environmental Protection Agency, 1996. Review of the
National Ambient Air Quality Standards for Particulate Matter:
Policy Assessment of Scientific and Technical Information. OAQPS
Staff Paper. Research Triangle Park, NC: Office of Air Quality
Planning and Standards; Report No. EPA-45/R-96-013.
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[[Page 16009]]
b. SO2 and NOX as Precursors for PM 2.5 and
8-hour Ozone. Fine particles are emitted directly from emissions
sources and also can be formed in the atmosphere through the reaction
of gaseous precursors. Sulfur dioxide and nitrogen oxides are among the
primary precursors to the ``secondary'' formation of PM 2.5.
Eight-hour ozone is exclusively a secondary pollutant. Ozone is
formed by natural processes at high altitudes, in the stratosphere,
where it serves as an effective shield against penetration of harmful
solar UV-B radiation to the ground. The ozone present at ground level
as a principal component of photochemical smog is formed in sunlit
conditions through atmospheric reactions of two main classes of
precursor compounds: VOCs and NOX (mainly NO and
NO2). Nitrogen oxides are emitted by motor vehicles, power
plants, and other combustion sources, with lesser amounts from natural
processes including lightning and soils.
Both PM 2.5 and 8-hour ozone are regional phenomena; that is each
is caused by emissions over a broad geographic area. As a result,
attainment of the PM 2.5 NAAQS requires reductions in SO2
and NOX over a widespread area, and attainment of the 8-hour
ozone NAAQS requires reductions in NOX over a widespread
area. In the CAIR proposal, EPA described the photochemistry and need
for regionwide reductions of precursors of both pollutants in detail.
See 69 FR at 4572.
After promulgation of the PM 2.5 NAAQS, EPA was generally aware of
the role of SO2 and NOX emissions in the PM 2.5
nonattainment problem, and, therefore, of the need for widespread
reductions. Similarly, after promulgation of the 8-hour ozone NAAQS,
EPA was aware of widespread nonattainment, due to nonattainment of the
pre-existing, one-hour ozone standard, and therefore of the need for
widespread NOX reductions.
c. Coal-fired Utility Units Emit A Large Portion of SO2
and NOX Emissions. Utility Units emit a large portion of
both the SO2 and NOX inventory. Congress clearly
recognized that the utility industry emits a large portion of the
nation's inventory of SO2 and NOX emissions when
Congress enacted the acid deposition provisions in the 1990 Clean Air
Act Amendments. EPA noted in the CAIR proposal that Utility Units--
are the most significant source of SO2 emissions and a
very substantial source of NOX in the * * * region
[proposed to be affected by CAIR]. For example, EGUs [Utility Units]
emissions are projected to represent approximately one-quarter (23
percent) of the total NOX emissions in 2010 and over two-
thirds (67 percent) of the total emissions in 2010 in the 28-State
plus DC region that [EPA proposed for] being controlled for both
SO2 and NOX after application of current CAA
controls.
(See 69 FR 4565, 4609-10 January 30, 2004.)
Beginning in the mid-1990s, EPA has considered regional and
national strategies to reduce interstate transport of SO2
and NOX. EPA described these efforts in the CAIR notice of
final rulemaking.
3. Legal Authority
As noted above, in 1997, EPA revised the NAAQS for PM to add new
annual average and 24-hour standards for fine particles, using PM 2.5
as the indicator (62 FR 38652). At the same time, EPA issued its final
action to revise the NAAQS for ozone to establish new 8-hour standards
(62 FR 38856.) Following promulgation of new NAAQS, the CAA requires
all areas, regardless of their designation as attainment,
nonattainment, or unclassifiable, to submit SIPs containing provisions
specified under section 110(a)(2). SIPs for nonattainment areas are
generally required to include additional emissions controls providing
for attainment of the NAAQS. In addition, under the authority of
section 110(a)(2)(D) and other provisions of section 110, EPA
promulgated the NOX SIP-Call in 1998. In that rulemaking,
EPA determined that 22 States and the District of Columbia in the
eastern half of the country significantly contribute to 1-hour and 8-
hour ozone nonattainment problems in downwind States.\35\ This rule
required those jurisdictions to revise their SIPs to include
NOX control measures to mitigate the significant ozone
transport. The EPA determined the emissions reductions requirements by
projecting NOX emissions to 2007 for all source categories
and then reducing those emissions through controls that EPA determined
to be highly cost-effective. The affected States were required to
submit SIPs providing the resulting amounts of emissions reductions.
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\35\ See ``Finding of Significant Contribution and Rulemaking
for Certain States in the Ozone Transport Assessment Group Region
for Purposes of Reducing Regional Transport of Ozone; Final Rule,''
63 FR 57356 (October 27, 1998). The EPA also published two Technical
Amendments revising the NOX SIP Call emission reduction
requirements. (64 FR 26298; May 14, 1999 and 65 FR 11222; March 2,
2000).
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Under the NOX SIP-Call, States had the flexibility to
determine the mix of controls to meet their emissions reductions
requirements. However, the rule provided that if the SIP controls
Utility Units, then the SIP must establish a budget, or cap, for
Utility Units. The EPA recommended that each State authorize a trading
program for NOX emissions from Utility Units. We developed a
model cap and trade program that States could voluntarily choose to
adopt, and all did so.
4. CAIR
In CAIR, EPA established SIP requirements for the affected upwind
States under the authority of CAA section 110(a)(2)(D) and other
provisions of section 110.\36\ Based on air quality modeling analyses
and cost analyses, EPA concluded that SO2 and NOX
emissions in certain States in the eastern part of the country, through
the phenomenon of air pollution transport, contribute significantly to
downwind nonattainment of the PM 2.5 and 8-hour ozone NAAQS. In CAIR,
EPA required SIP revisions in 28 States and the District of Columbia to
reduce SO2 and/or NOX emissions, which are
important precursors of PM 2.5 (NOX and SO2) and
ozone (NOX). The affected States and the District of
Columbia are required to adopt and submit the required SIP revision
with the necessary control measures by 18 months from date of signature
of CAIR.
The 23 States along with the District of Columbia that must reduce
annual NOX emissions for the purposes of the PM 2.5 NAAQS
are: Alabama, Florida, Georgia, Illinois, Indiana, Iowa, Kentucky,
Louisiana, Maryland, Michigan, Minnesota, Mississippi, Missouri, New
York, North Carolina, Ohio, Pennsylvania, South Carolina, Tennessee,
Texas, Virginia, West Virginia, and Wisconsin.
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\36\ See ``Rule to Reduce Interstate Transport of Fine
Particulate Matter and Ozone (Interstate Air Quality Rule); Proposed
Rule,'' 69 FR 4566 (January 30, 2004); ``Supplemental Proposal for
the Rule to Reduce Interstate Transport of Fine Particulate Matter
and Ozone (Clean Air Interstate Rule); Proposed Rule,'' 69 FR 32684
(June 10, 2004); and the final rule ``Rule to Reduce Interstate
Transport of Fine Particulate Matter and Ozone (Clean Air Interstate
Rule),'' which was recently issued.
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The 25 States along with the District of Columbia that must reduce
NOX emissions for the purposes of the 8-hour ozone NAAQS
are: Alabama, Arkansas, Connecticut, Delaware, Florida, Illinois,
Indiana, Iowa, Kentucky, Louisiana, Maryland, Massachusetts, Michigan,
Mississippi, Missouri, New Jersey, New York, North Carolina, Ohio,
Pennsylvania, South Carolina,
[[Page 16010]]
Tennessee, Virginia, West Virginia, and Wisconsin.
The emissions reductions requirements are based on controls that
EPA determined to be highly cost-effective for Utility Units. However,
States have the flexibility to choose the measures to adopt to achieve
the specified emissions reductions. If the State chooses to control
Utility Units, then it must establish a budget--that is, an emissions
cap--for those sources. CAIR defines the Utility Units budgets for each
affected State. Due to feasibility constraints, EPA is requiring that
emissions reductions be implemented in two phases, with the first phase
in 2009 (for NOX) and 2010 (for SO2), and the
second phase in 2015.
As noted above, under the CAIR, each State may independently
determine which emissions sources to subject to controls, and which
control measures to adopt. The EPA's analysis indicates that emissions
reductions from Utility Units are highly cost-effective, and in the
CAIR, EPA encouraged States to adopt controls for Utility Units. States
that do so must place an enforceable limit, or cap, on Utility Unit's
emissions. The EPA calculated the amount of each State's Utility Unit
emissions cap, or budget, based on reductions that EPA determined are
highly cost-effective. States may allow their Utility Units to
participate in an EPA-administered cap-and-trade program as a way to
reduce the cost of compliance, and to provide compliance flexibility.
The EPA will administer these programs, which will be governed by rules
provided by EPA that States may adopt or incorporate by reference.
EPA estimated that the CAIR would reduce annual SO2
emissions by 3.6 million tons by 2010 and by 4.0 million tons by 2015;
and would reduce annual NOX emissions by 1.3 million tons by
2010 and by 1.5 million tons by 2015. If all the affected States choose
to achieve these reductions through Utility Unit controls, then Utility
Unit emissions in the affected States would be capped at 3.7 million
tons in 2010 and 2.6 million tons in 2015; and Utility Unit annual
NOX emissions would be capped at 1.5 million tons in 2010
and 1.3 million tons in 2015. The EPA estimated that the required
SO2 and NOX emissions reductions would, by
themselves, bring into attainment 52 of the 80 counties that are
otherwise expected to be in nonattainment for PM 2.5 in 2010, and 57 of
the 75 counties that are otherwise expected to be in nonattainment for
PM 2.5 in 2015. The EPA further estimated that the required
NOX emissions reductions would, by themselves, bring into
attainment 3 of the 40 counties that are otherwise expected to be in
nonattainment for 8-hour ozone in 2010, and 6 of the 22 counties that
are expected to be in nonattainment for 8-hour ozone in 2015. In
addition, the CAIR would improve PM 2.5 and 8-hour ozone air quality in
the areas that would remain nonattainment for those two NAAQS after
implementation of CAIR. Because of the CAIR, the States with those
remaining nonattainment areas will find it less burdensome and less
expensive to reach attainment by adopting additional local controls.
The CAIR would also reduce PM 2.5 and 8-hour ozone levels in attainment
areas.
C. Utility Mercury Emission Reductions Expected as Co-Benefits From
CAIR
The final CAIR requires annual SO2 and NOX
reductions in 23 States and the District of Columbia, and also requires
ozone season NOX reductions in 25 States and the District of
Columbia. Many of the CAIR States are affected by both the annual
SO2 and NOX reduction requirements and the ozone
season NOX requirements. CAIR was designed to achieve
significant emissions reductions in a highly cost-effective manner to
reduce the transport of fine particles that have been found to
contribute to nonattainment. EPA analysis has found that the most
efficient method to achieve the emissions reduction targets is through
a cap-and-trade system on the power sector that States have the option
of adopting. In fact, States may choose not to participate in the
optional cap-and-trade program and may choose to obtain equivalent
emissions reductions from other sectors. However, EPA believes that a
region-wide cap-and-trade system for the power sector is the best
approach for reducing emissions. The power sector accounted for 67
percent of nationwide SO2 emissions and 22 percent of
nationwide NOX emissions in 2002.
EPA expects that States will choose to implement the final CAIR
program in much the same way they chose to implement their requirements
under the NOX SIP Call. As noted above, under the
NOX SIP Call, EPA gave States ozone season NOX
reduction requirements and the option of participating in a cap-and-
trade program. In the final rulemaking, EPA analysis indicated that the
most efficient method to achieve reductions targets would be through a
cap-and-trade program. Each affected State, in its approved SIP, chose
to control emissions from Utility Units and to participate in the cap-
and-trade program.
Therefore, EPA anticipates that States will comply with CAIR by
controlling Utility Unit SO2 and NOX emissions.
Further, EPA anticipates that States will implement those reductions
through the cap-and-trade approach, since the power sector represents
the majority of national SO2 emissions and the majority of
stationary NOX emissions, and represent highly cost-
effective SO2 and NOX sources to reduce. For
further discussion of cost-effectiveness, see section IV of CAIR notice
of final rulemaking. EPA modeled a region-wide cap and trade system on
the power sector for the States covered by CAIR, and this modeling
projected that most reductions in NOX and SO2
would come through the installation of scrubbers, for SO2
control, and selective catalytic reduction for NOX control
(see Regulatory Impact Assessment for CAIR and CAMR in docket).
Scrubbers and SCR are proven technologies for controlling
SO2 and NOX emissions and sources installed them
to comply with the Acid Rain trading program and the NOX SIP
Call trading program. EPA's modeling also projected that the
installation of these controls would achieve Hg emission reductions as
a co-benefit.
EPA projections of Hg co-benefits are based on 1999 Hg ICR emission
test data and other more recent testing conducted by EPA, DOE, and
industry participants. (For further discussion see Control of Emissions
from Coal-Fired Electric Utility Boilers: An Update, EPA/Office of
Research and Development, March 2005, in the docket). That emission
testing has provided a better understanding of Hg emissions and their
capture in pollution control devices. Mercury speciates into three
basic forms, ionic, elemental, and particulate (particulate represents
a small portion of total emissions). In general, ionic Hg compounds are
more readily absorbed than elemental Hg and the presence of chlorine
compounds (which tend to be higher for bituminous coals) results in
increased ionic Hg. Overall the 1999 Hg ICR data revealed higher levels
of Hg capture for bituminous coal-fired plants as compared to
subbituminous and lignite coal-fired plants and a significant capture
of ionic Hg in wet SO2 scrubbers. Additional Hg testing
indicates that for bituminous coals SCR has the ability to convert
elemental Hg to ionic Hg and thus allow easier capture in a wet
scrubber. This understanding of Hg capture was incorporated into EPA
modeling assumptions and is the basis for our projections of Hg co-
benefits from installation of scrubbers and SCR under CAIR.
The final CAIR requires annual SO2 and NOX
reductions in two phases, the
[[Page 16011]]
first phase in 2010 and the second phase in 2015. EPA modeling of CAIR
projected that most reductions in NOX and SO2
would come through the installation of scrubbers and SCR, and that the
installation of these controls would also achieve Hg emission
reductions as a co-benefit. Given the history of the Acid Rain and
NOX SIP Call trading programs, and our experience with those
programs, we anticipate that reductions in SO2 emissions
will begin to occur before 2010 because of the ability to bank
SO2 emission allowances, though to some degree this is
limited by the time and resources needed to install control
technologies. Companies have an incentive to achieve greater
SO2 reductions than needed to meet the current Acid Rain cap
because the excess allowances they generate can be ``banked'' and
either later sold on the market or used to demonstrate compliance in
2010 and beyond at the facility that generated the excess allowances.
Based on the analysis of CAIR, EPA's modeling projects that Hg
emissions would be 38.0 tons (12 tons of non-elemental Hg) in 2010,
34.4 tons in 2015 (10 tons of non-elemental Hg), and 34.0 tons in 2020
(9 tons of non-elemental Hg), about a 20 and 30 percent reduction (in
2010 and 2015, respectively) from a 1999 baseline of 48 tons.\37\ For
further discussion of EPA modeling results and projected emissions see
Chapter 8 of the Regulatory Impact Assessment.\38\
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\37\ As discussed in the TSD, the emissions of reactive gaseous
Hg and particle-bound Hg are most important for local and regional
Hg deposition purposes, since they are substantially more likely to
be deposited than elemental Hg. CAIR and CAMR will significantly
reduce reactive gaseous Hg and particle bound Hg from 2001 levels.
CAIR will reduce the levels from approximately 22 tons to 9 tons.
CAMR will reduce this level further to between 7 and 9 tons, for a
total reduction (with CAIR) of roughly 70 percent.
\38\ In addition to CAIR, EPA recently promulgated another rule
for Utility Units. Specifically, on March 15, 2005, the
Administrator signed a final rulemaking called the Clean Air Mercury
Rule (``CAMR'') pursuant to CAA section 111. This rule sets
standards of performance for Hg emitted from both new and existing
coal-fired Utility Units. Like CAIR, the rule establishes a cap-and-
trade mechanism by which Hg emissions from new and existing coal-
fired Utility Units are capped at specified, nation-wide levels. The
first phase cap of 38 tons per year (``tpy'') becomes effective in
2010 and the second phase cap of 15 tpy becomes effective in 2018.
Facilities must demonstrate compliance with the standards of
performance by holding one ``allowance'' for each ounce (oz) of Hg
emitted in any given year. Allowances are readily transferrable
among all regulated units. As explained in section VI below, the
level of Hg emissions remaining after implementation of CAMR do not
result in hazards to public health.
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VI. Scientific and Technical Background and EPA'S Conclusions
Concerning the Level of Utility Attributable Mercury Emissions After
CAIR and CAMR
In this section, we explain why we believe the level of utility
attributable Hg emissions remaining after imposition of CAIR, and
independently, CAMR, will not result in hazards to public health. The
issue of whether utility Hg emissions remaining after CAIR, and
independently CAMR, result in hazards to public health is directly
related to our conclusion, stated above in Section IV.A, that we cannot
find it appropriate and necessary to regulate coal-fired Utility Units
under section 112 on the basis of Hg emissions. This section includes
an overview of the scientific and technical information relevant to
evaluating utility Hg emissions and the public health impacts
associated with such emissions. Below, we provide general background
concerning the health impacts of methylmercury; the predominant
exposure pathway by which humans are affected by methylmercury, which
is by ingestion of fish containing methylmercury; and EPA's methodology
for determining the impacts of utility Hg emissions on the amount of
methylmercury found in fish tissue. This section also includes a
summary of our conclusions, including that utility Hg emissions
remaining after implementation of CAIR, and independently CAMR, are not
reasonably anticipated to result in hazards to public health.
A. Human Health Impacts of Methylmercury Exposure and Amounts of Hg
Emissions
Hg is a persistent, bioaccumulative toxic metal that is emitted
from power plants in three forms: Elemental mercury (Hg\0\), oxidized
mercury (Hg\++\) compounds, as well as particle-bound mercury.
Methylmercury is formed by microbial action in the top layers of
sediment and soils, after Hg has precipitated from the air and
deposited into water bodies or land. Once formed, methylmercury is
taken up by aquatic organisms and bioaccumulates up the aquatic food
web. Larger predatory fish may have methylmercury concentrations many
times that of the water body in which they live.
While Hg is toxic to humans when it is inhaled or ingested, we
focus on oral exposure of methylmercury in this rulemaking, as it is
the route of primary interest for human exposures in the U.S.
Methylmercury is a well-established human neurotoxicant. Methylmercury
that is ingested by humans is readily absorbed from the
gastrointestinal tract and can cause effects in several organ systems.
The best studied effect of low level exposure is the ability of
methylmercury to cause subtle, yet potentially important
neurodevelopmental effects. Of particular concern is the effect of
methylmercury on the developing fetal nervous system exposed in utero
from maternal fish ingestion. Large prospective epidemiological studies
have reported that prenatal methylmercury from environmental exposures
has been associated with poor performance on neurobehavioral tests in
children. These include tests that measure attention, visual-spatial
ability, verbal memory, language skills, and fine motor function. These
studies have been thoroughly reviewed, singly and as part of review
groups, by many expert scientists, including a panel of the National
Research Council (NRC) of the National Academy of Sciences (NAS).\39\
While important, the weight of evidence for cardiovascular effects is
not as strong as it is for childhood neurological effects and the state
of the science is still being evaluated. However, some recent
epidemiological studies in men suggest that methylmercury is associated
with a higher risk of acute myocardial infaraction, coronary heart
disease and cardiovascular disease in some populations. Other recent
studies have not observed this association. The findings to date and
the plausible biological mechanisms warrant additional research in this
area (Stern 2005; Chan and Egeland 2004). There is some recent evidence
that methylmercury may result in genotoxic or immunotoxic effects.
Overall, there is a relatively small body of evidence from human
studies that suggests exposure to methylmercury can result in
immunotoxic effects and the NRC concluded that evidence that human
exposure caused genetic damage is inconclusive. There are insufficient
human data to evaluate whether these effects are consistent with levels
in the U.S. population. Because the developing fetus may be the most
sensitive to the effects from methylmercury, women of
[[Page 16012]]
child-bearing age are regarded as the population of greatest interest
when assessing methylmercury exposure.
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\39\ Studies investigating the relationship between
methylmercury and cardiovascular effects have reached different
conclusions. Some recent epidemiological studies of men suggest that
methylmercury is associated with a higher risk of acute myocardial
infarction, coronary heart disease and cardiovascular disease in
some populations. Other research with less corroboration suggest
that reproductive, renal, and hematological impacts may be of
concern. There are insufficient human data to evalaute whether these
effects are consistent with levels in the U.S. population. See RIA
for CAMR chapter 2.
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The predominant pathway of Hg exposure to both humans and wildlife
is consumption of fish. Critical elements in estimating methylmercury
exposure and risk from fish consumption include the concentrations of
methylmercury in the fish consumed, the quantity of fish consumed,\40\
and how frequently the fish is consumed. There is a great deal of
variability among individuals in fish consumption rates. However, our
analysis indicates that the typical U.S. consumer eating moderate
amounts of a wide variety of low-mercury fish from restaurants and
grocery stores is not expected to ingest harmful levels of
methylmercury from fish. Those who regularly and frequently consume
large amounts of fish, or fish with higher levels of methylmercury, are
more exposed. The EPA and Food and Drug Administration jointly, as well
as states, have issued fish consumption advisories to inform people of
ways to reduce exposure to methylmercury from fish.
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\40\ A precise estimate of methylmercury exposure depends on
quantity of fish consumed as a function of an individual's body
weight.
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As part of its long term U.S. population surveillance, the U.S.
Centers for Disease Control (CDC) assessed Hg concentrations in blood
of over 3,600 women of child-bearing age under the National Health and
Nutrition Examination Survey (NHANES). A recent analysis of these data
reported that about 6 percent of these women of child-bearing age have
levels of Hg in their blood that are at or above the U.S. EPA's RfD,
described below. The CDC also surveyed the same group of women about
their eating habits. An analysis of 1500 of these women showed that Hg
blood levels were higher in the women who reported eating three or more
servings of fish in the month before they were tested. It is reasonable
to conclude that methylmercury contained in seafood may be responsible
for elevated levels of Hg in U.S. women of child-bearing age.\41\
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\41\ 289 JAMA 1667 (April 2, 2003).
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As described below, the analysis supporting today's action focuses
on assessing exposure from freshwater fish caught and consumed by
recreational and subsistence anglers because available information
indicate that U.S. utility Hg emissions may affect the methylmercury
concentrations in these fish. EPA also considered the following fish
consumption pathways: Consumption from commercial sources (including
saltwater and freshwater fish from domestic and foreign producers);
consumption of recreationally caught marine fish, consumption of
recreationally caught estuarine fish; and consumption of commercial
fish raised at fish farms (aquaculture). For a number of reasons, as
explained in the TSD, current information does not suggest that these
latter pathways present meaningful risks of ingestion of utility-
attributable methylmercury.
The EPA's 1997 Mercury Study Report to Congress suggests a
plausible link between anthropogenic releases of Hg from industrial and
combustion sources in the U.S. and methylmercury in fish in the U.S.
However, other sources of Hg emissions, including Hg from natural
sources (such as volcanos) and anthropogenic emissions in other
countries, contribute to the levels of methylmercury observed in fish
in the U.S.\42\ Our current understanding of the global Hg cycle and
the impact of the anthropogenic sources allow us to make estimates on a
global, continental, or regional scale of their relative importance. It
is more difficult to make accurate predictions of the fluxes on a local
scale given our current understanding.
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\42\ Recent Hg estimates (which are highly uncertain) of annual
total global emissions from all sources (natural and anthropogenic)
are about 5,000 to 5,500 tons per year (tpy). Of this total, about
1,000 tpy are estimated to be natural emissions and about 2,000 tpy
are estimated to be contributions through the natural global cycle
of re-emissions of Hg associated with past natural releases and
anthropogenic activity. Current anthropogenic emissions account for
the remaining 2,000 tpy. Given the global estimates noted above,
U.S. anthropogenic Hg emissions are estimated to account for roughly
3 percent of the global total, and U.S. utilities are estimated to
account for about 1 percent of total global emissions. Deposition
from U.S. utilities is described in greater detail below. Utility
RTC at 7-1 to 7-2; Mercury NPR, 69 FR 4657-58 (January 20, 2004);
RIA for CAMR chapters 5-6.
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We recognize that it is also difficult to quantify with precision
how a specific change in air deposition of Hg leads to a change in fish
tissue levels. We further recognize that the relationship between the
amount of Hg emissions reduced and the attendant reduction in
methlymercury fish concentrations depends upon the specific
characteristics of the waterbody at issue. Nevertheless, science
continues to evolve and EPA has made substantial progress in developing
methods for assessing the amount of methylmercury in fish tissues that
may be traced to emissions from coal-fired U.S. Utility Units. We
describe our methodology below and why this methodology is sufficient
to support today's action.
As discussed above, we are focusing on consumption of self-caught,
freshwater fish. We estimate that there are approximately 27.9 million
recreational freshwater fishers in the U.S. population, including
fishers who do not eat (e.g., release) their catch. Based on
application of a ``consuming'' factor and a ``sharing'' factor to the
estimate of recreational fishers, as discussed further in the RIA to
CAMR, we estimate that approximately 58.6 million individuals in the
U.S. population consume recreationally-caught freshwater fish. Of these
individuals, we estimate that approximately 7.5 to 10.5 million are
women of child-bearing age (that is, 15-44 years old), about 500,000 of
whom are expected to give birth in any one year. We estimate that the
mean recreational freshwater fish consumption rate for these women is 8
grams/day, and the 95th percentile recreational freshwater fish
consumption rate is 25 grams/day. A subset of recreational freshwater
fish consumers may consume at higher levels, as discussed below. In
addition, subsistence fishers and fishers in certain ethnic groups are
expected to have generally higher fish consumption rates than consumers
of recreational freshwater fish. These sub-populations are discussed
below.
B. The Methylmercury Reference Dose
EPA generally quantifies risk of adverse health effects other than
cancer by calculating a reference value (RfV). In general, an RfV is an
estimation of an exposure that is likely to be without an appreciable
risk of adverse effects over a lifetime. See http://www.epa.gov/iris/gloss8.htm. RfVs for exposure by ingestion are called reference doses
(RfD).
The EPA defines an RfD as ``an estimate (with uncertainty spanning
perhaps an order of magnitude) of a daily oral exposure to the human
population (including sensitive subgroups) that is likely to be without
an appreciable risk of deleterious effects during a lifetime. It can be
derived from a NOAEL (no observed adverse effect level), LOAEL (lowest
observed adverse effect level), or benchmark dose, with uncertainty
factors generally applied to reflect limitations of the data used.''
See http://www.epa.gov/iris/gloss8.htm.
As stated above, an RfD is derived by choosing a point of departure
from animal or human data. This can be a NOAEL or LOAEL, either of
which may be defined by applying statistical tests and scientific
judgment to the data. When the data are sufficient, one can apply a
mathematical model to obtain a benchmark dose (BMD). The BMD is the
dose at which a particular level of response (i.e., the benchmark
response,
[[Page 16013]]
or BMR) for some outcome of concern is found to occur. One can then
derive a BMD lower confidence limit (BMDL), which is a statistical
lower bound on the chosen BMD, an exposure expected to produce a
specified effect in some defined percentage of a test population.
The point of departure (again, NOAEL, LOAEL, or BMDL) is divided by
uncertainty/variability factors to arrive at the RfD. The uncertainty
factors are intended to account for variability and uncertainty in the
data. The size of an uncertainty/variability factor is determined by
the adequacy or limitations of the data and is typically either 10 or 3
for each type of variabilty. For example, uncertainty factors may be
employed for extrapolating from animals to humans, variability in human
susceptibility (sensitive populations), and extrapolating from
subchronic to chronic exposures. The resulting RfD is believed to be
the amount of a chemical which, when ingested daily over a lifetime, is
likely to be without an appreciable risk of deleterious effects to
humans, including sensitive subpopulations.
In 2001, EPA published an RfD for methylmercury that is based on a
BMD approach. This quantitative risk estimate was based on data from
developmental neurotoxicity studies mentioned above; specifically,
deficits in tests associated with ability to learn and process
information. EPA applied an uncertainty/variability factor of 10 to the
point of departure (BMDL) to derive the RfD. EPA's RfD for
methylmercury is 0.1 [mu]g/kg bw/day, which is 0.1 micrograms of Hg per
day for each kilogram of a person's body weight.
As noted in the Hg Proposal, at the direction of Congress, EPA
funded the NAS to perform an independent evaluation of the available
data related to the health impacts of methylmercury and provide
recommendations for EPA's RfD. The NAS/National Research Council (NRC)
conducted an 18-month study of the available data on the health effects
of methylmercury. The review by the NAS, published in July 2000,
concluded that the neuro-developmental effects are the most sensitive
and well-documented effects of methylmercury exposure. The NRC advised
revising the basis of the RfD, which used data from a short-term
exposure in Iraq, to incorporate new studies on children exposed in
utero when their mothers ate seafood containing Hg. EPA subsequently
established a reference dose of 0.0001 mg/kg bw/day. NAS determined
that EPA's RfD ``is a scientifically justified level for the protection
of public health.''
The methylmercury RfD is further described in the RIA, chapter 2
and in other EPA documents (IRIS, U.S. EPA 2001; Water Quality Criteria
for the Protection of Human Health: Methylmercury, EPA-823-R-01-001).
Briefly, EPA used as the point of departure BMDLs for multiple
endpoints from the three studies of in utero methylmercury exposure and
effects. These were conducted in the Faroes and Seychelles Islands and
in New Zealand.\43\ All of the endpoints were children's scores on
neuropsychological tests. Consistent with NRC recommendations, an
uncertainty/variability factor of 10 was used to account for
pharmacokinetic and pharmacodynamic variability in the human
population. In the EPA documents, one data set from the Faroes (Boston
Naming Test, full cohort) is displayed for all calculations as an
example of the multiple BMDLs which serve as the basis for the RfD.
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\43\ More specifically, the subjects of the Seychelles
longitudinal prospective study were 779 mother-infant pairs from a
fish-eating population (Myers et al., 1995a-c, 1997; Davidson et
al., 1995, 1998). Infants were followed from birth to 5.5 years of
age, and assessed at various ages on a number of standardized
neuropsychological endpoints. The independent variable was maternal-
hair Hg levels. The Faroe Islands study was a longitudinal study of
about 900 mother-infant pairs (Grandjean et al., 1997). The main
independent variable was cord-blood Hg; maternal-hair Hg was also
measured. At 7 years of age, children were tested on a variety of
tasks designed to assess function in specific behavioral domains.
The New Zealand study was a prospective study in which 38 children
of mothers with hair Hg levels during pregnancy greater than 6 ppm
were matched with children whose mothers had lower hair Hg levels
(Kjellstrom et al., 1989, 1986). At 6 years of age, a total of 237
children were assessed on a number of neuropsychological endpoints
similar to those used in the Seychelles study (Kjellstrom et al.,
1989). The Seychelles study yielded no statistically significant
evidence of impairment related to in utero methylmercury exposure,
whereas the other two studies found dose-related effects on a number
of neuropsychological endpoints. In the assessment described here,
an integrative analysis of all three studies was relied upon in
setting the point of departure for derivation of the RfD. As noted
by NRC in reference to data from the Seychelles, Faroe Islands, and
New Zealand, ``because those data are epidemiological, and exposure
is measured on a continuous scale, there is no generally accepted
procedure for determining a dose at which no adverse effects
occur.'' (NRC 2000)
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In determining the RfD for methylmercury, EPA said that the ``RfD
can be considered a threshold for a population at which it is unlikely
that adverse effects will be observed'' (Water Quality Criteria for the
Protection of Human Health: Methylmercury, EPA-823-R-01-001). The RfD
was calculated to be a level ``likely to be without an appreciable
risk,'' of ``deleterious effects'' for all populations, including
sensitive subgroups. EPA does not further quantify the degree of risk
which would be expected for exposures at or above the methylmercury
RfD. This is the case for all of EPA's RfDs. Additional regulatory
values support a similar threshold approach for describing risks to
methylmercury exposure. For example, the World Health Organization sets
the level at 0.23 [mu]g/kg/day; Health Canada sets the level at 0.2
[mu]g/kg/day; and the Agency for Toxic Substances and Disease Registry
(ATSDR) sets a value of 0.3 [mu]g/kg/day.
EPA has established the RfD at a level such that exposures at or
below the RfD are unlikely to be associated with appreciable risk of
deleterious effects. It is important to note, however, that the RfD
does not define an exposure level corresponding to zero risk; exposure
near or below the RfD could pose a very low level of risk which EPA
deems to be non-appreciable. It is also important to note that the RfD
does not define a bright line, above which individuals are at risk of
adverse effects.
Further, in EPA's 1989 Residual Risk Report to Congress, we stated:
It should be noted that exposures above an RfD or RfC do not
necessarily imply unacceptable risk or that adverse health effects
are expected. Because of the inherent conservatism of the RfC/RfD
methodology, the significance of exceedances must be evaluated on a
case-by-case basis, considering such factors as the confidence level
of the assessment, the size of UF used, the slope of the dose-
response curve, the magnitude of the exceedance, and the number or
types of people exposed at various levels above the RfD or RfC.\44\
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\44\ U.S. Environmental Protection Agency. 1989. Risk Assessment
Guidance for Superfund: Volume I. Human Health Evaluation Manual
(Part A). Office of Emergency and Remedial Response. Washington, DC,
EPA/541/1-89/002, at 52-53 http://www.epa.gov/oswer/riskassessment/ragsa/pdf/ch8.pdf (Residual Risk Report). The Residual Risk Report
further stated:
It is expected that an HI (i.e., hazard index (HI)), which is
the sum of more than one hazard quotient for multiple substances
and/or multiple exposure pathways) less than 1 that is derived using
target organ specific hazard quotients would ordinarily be
considered acceptable. If the HI is greater than 1, then the amount
by which the HI is greater than 1, the uncertainty in the HI, the
slope of the dose-response curve, and a consideration of the number
of people exposed would be considered in determining whether the
risk is acceptable. Evaluation of the acceptable value for an HQ
(i.e., hazard quotient (HQ), which is the ratio of the exposure
level to a reference exposure level (e.g., RfD)) or an HI of 1 also
would consider the values of UFs (i.e., uncertainty/variability
factor (UF)), which is a default factor--generally 10-fold--used in
operationally deriving the RfD or RfC from experimental data) and
the confidence in the RfC that are used in the calculation of the
HI. In general, it is considered that each UF is somewhat
conservative; because all factors are not likely to simultaneously
be at their most extreme (highest) value, a combination of several
factors can lead to substantial conservatism in the final value.
Larger composite UF lead to more conservative RfC. Conversely, lower
composite UF are less conservative and usually indicate a higher
level of confidence in the RfC. Intermediate UF values or a mixture
of high and low UF would require an examination of the relative
contribution of various chemicals to the HI. Thus, an HI or HQ
greater than 1 may be considered acceptable based on consideration
of other factors.
Id. at 125.
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[[Page 16014]]
C. Methylmercury Levels in Fish and the Methylmercury Water Quality
Criterion
As noted above, the most important pathway of exposure to Hg for
humans is through the consumption of fish and seafood. These include
saltwater fish such as tile fish, shark, and swordfish, which are most
often caught commercially. They also include freshwater fish such as
bass, perch, and walleye, which are often caught recreationally,
commercially, or for personal consumption or distribution. Generally
shellfish have lower levels of methylmercury than do finfish. The
levels of Hg in fish and shellfish are variable, with mean levels
ranging from non-detectable to 1.45 mg/kg, depending on species. See
FDA Mercury Levels in Commercial Fish and Shellfish (http://
www.cfsan.fda.gov/frf/sea-mehg.html).
Methylmercury exposure is a function of how much fish is eaten (on
a bodyweight basis), how frequently fish is eaten, and the
methylmercury concentration in the fish. As a result, estimates of the
amount and type of fish consumption are important to assessing the
impacts of methylmercury attributed to coal-fired Utility Units on
public health.
Hg is emitted from powerplants in three forms: Elemental Hg,
reactive (oxidized) Hg, and particulate Hg. Most of the local and
regional Hg deposition is associated with the emissions of reactive Hg.
For this reason, the magnitude of reactive Hg emission from powerplants
is critical to Hg deposition in the United States. As noted above, FGD
and SCR control technologies are most effective in controlling reactive
Hg emissions. As indicated by Table VI-2, roughly 90 percent of the Hg
reductions under CAIR in 2020 are reactive Hg. As a result, the
SO2 and NOX limits established by CAIR yield
significant reductions (roughly 70 percent) in reactive Hg emissions
from powerplants.
Americans eat fish from a variety of sources. An individual's fish
diet can be composed of commercial fish and shellfish (both imported
and domestic), fish from aquaculture (or farm raised fish for
commercial sale), and fish from non-commercial sources (e.g.,
recreationally caught fish, fish caught to meet dietary needs, and/or
fish caught for cultural or traditional reasons). These fish may come
from marine, estuarine, or freshwater sources.
Using the 2001 RfD and information on Hg exposure routes, EPA
published a recommended ambient water quality criterion for the states'
and tribes' use in setting water quality standards for U.S. waters
(freshwater and estuarine) that are designed to protect human health.
EPA issued the methylmercury water quality criterion in 2001. Water
Quality Criterion for the Protection of Human Health: Methylmercury.
EPA-823-R-01-001. Office of Science and Technology, Office of Water,
USEPA, Washington, DC, USEPA 2001) Because of the wide variability in
methylmercury bioaccumulation among waterbodies, EPA set the criterion
as a fish tissue level rather than as an ambient water concentration.
The criterion is 0.3 mg/kg (milligram methylmercury per kilogram of
wet-weight fish tissue). The criterion is a risk assessment number that
states and authorized tribes may use in their programs for protection
of designated uses.
The Clean Water Act (CWA) and EPA's regulations specify
requirements for adoption of water quality criteria. States and
authorized tribes must adopt water quality criteria that protect
designated uses. See CWA section 303(c)(2)(A). Water quality criteria
must be based on a sound scientific rationale and must contain
sufficient parameters or components to protect the designated uses. See
40 CFR 131.11. States and authorized tribes must adopt criteria for all
toxic pollutants where EPA has established ambient water quality
criteria where the discharge or presence of these pollutants could
reasonably interfere with the designated uses. See CWA Section
303(c)(2)(B). EPA issued guidance on how states and authorized tribes
may comply with section 303(c)(2)(B) which is now contained in the
Water Quality Standards Handbook: Second Edition (EPA, 1994). States
and authorized tribes that decide to use the recommended methylmercury
criterion as the basis for new or revised methylmercury water quality
standards have the option of adopting the criterion as a fish tissue
concentration into their water quality standards, adjusting the
criterion to account for state or local exposure, or adopting it as a
traditional water column concentration. States and authorized tribes
remain free not to use EPA's current recommendations, provided that
their new or revised water quality criteria for methylmercury protect
the designated uses and are based on a scientifically defensible
methodology.
The methylmercury water quality criterion incorporated the RfD,
data on freshwater and estuarine finfish and shellfish consumption for
the target population (the adult general population), and information
on exposure to methylmercury as a result of consumption of marine fish
(for methylmercury, exposure from any route other than eating fish is
negligible). Specifically, EPA assumed a default intake of freshwater
and estuarine and marine finfish and shellfish of 17.5 grams per day
(or two 8-ounce meals a month) conforming to EPA's methodology. (EPA;
``Methodology for Deriving Ambient Water Quality Criteria for the
Protection of Human Health (2000),'' EPA-822-B-00-004 (October 2000)
(``2000 Water Quality Criteria Methodology'')). This default (to be
used by EPA for national criteria or others in the absence of data
specific to a waterbody) is the 90th percentile total (commercial and
non-commercial) freshwater and estuarine finfish and shellfish
consumption reported by adults, both consumers and non-consumers. The
source of this data is the 1994-1996 Continuing Study of Food Intake by
Individuals (CSFII). This is a large ongoing U.S. food consumption
survey conducted by USDA.
In addition, in accordance with EPA's published methodology, in
developing the criterion, EPA used a relative source contribution (RSC)
approach to apportion the RfD to ensure that the water quality
criterion is protective, given other sources of exposure. The RSC
approach apportions the RfD according to routes of exposures; for
methylmercury this adjustment was done to account for marine fish
consumption, as the criterion is for freshwater and estuarine finfish
and shellfish. In deriving the methylmercury water quality criterion,
EPA assumed an exposure to methylmercury in marine fish that is
equivalent to 27 percent of RfD. That is, EPA developed the criterion
so that it would be protective even if an individual is consuming
typical amounts of fish from other sources (i.e., marine fish).
D. EPA's Methodology for Assessing Methylmercury Levels in Fish Tissues
To estimate methylmercury levels, including methylmercury
attributable to Utility Units, in consumed freshwater fish, EPA's
analysis relied primarily on monitoring data (i.e., fish tissue samples
collected from freshwater sites across the study area). EPA used
sources of national-level monitored Hg data. The
[[Page 16015]]
National Listing of Fish and Wildlife Advisories (NLFA), which is
maintained by EPA, contains data from over 80,000 fish tissue samples
across the U.S. In addition to the NLFA, EPA's National Fish Tissue
Survey (NFTS) provides useful data. Conducted in 2000-2003, this
dataset includes fish tissue samples from 500 randomly selected lakes
and reservoirs across the U.S. EPA considers these combined two data
sets to be sufficiently comprehensive and sufficiently inclusive of the
waterbodies of highest exposure for use in EPA's regional analysis,
although, as discussed in the TSD, for certain areas of the country,
gaps in the datasets have led EPA to rely on overall regional trends to
draw conclusions for local areas.
The NLFA is the most extensive available source of fish tissue
sampling data for Hg. It currently includes fish tissue contaminant
data collected by states (and submitted to EPA) from over 10,000
locations nationwide, with most of the locations in the eastern half of
the U.S. In general, the States historically sampled waterbodies in
areas of suspected contamination. More recently, states have also
focused sampling efforts on areas of elevated fishing pressure. Almost
all of the tissue samples include tests for Hg. The NLFA includes
roughly 83,000 Hg samples collected in the U.S. between 1967 and 2002.
In the dataset, most samples are described according to the sample
location, sample date, measured Hg concentration, species and size of
fish, and the part of the fish sampled.
Based on the geographic coordinates provided in the NLFA database,
EPA also defined two additional fields for each Hg sample:
--The eight-digit watershed (hydrological unit code (HUC) (discussed
below)) in which the sample was located; and
--The type of waterbody (i.e., lake or river/stream) from which the
sample was taken.
The HUC, developed by the USGS, spatially delineates watersheds
throughout the United States. Hydrologic units are available at four
levels of aggregation, ranging from a two-digit regional level (21
units nationwide) to the eight-digit HUC (2,150 distinct units). The
eight-digit HUC-level designation is useful for this analysis because
it provides a nationally consistent approach for grouping waterbodies
on a ``local'' scale (the average HUC area is 1,631 sq mi).\45\
---------------------------------------------------------------------------
\45\ More information regarding these hydrological units can be
found through the USGS Web site http://water.usgs.gov/GIS/huc.html.
---------------------------------------------------------------------------
We made the water body type assignments using proximity analysis in
ArcINFO. Each sampling site was assigned to either a flowing (e.g.,
river, stream) or a stationary (e.g., lake, reservoir) waterbody,
according the type of waterbody most closely located to the site's lat/
long coordinates. We used National Hydrology Dataset (NHD) in the
proximity analysis.
For purposes of the modeling described below, we restricted the
samples selected from the NLFA data to those that met the following
criteria:
Collected after 1999;
Sampled from freshwater species (i.e., saltwater species
are excluded from the analysis); and
Sampled from freshwater (rather than estuarine or coastal)
waterbodies.
These NLFA Hg sampling data were supplemented with additional
observations from EPA's National Fish Tissue Survey (NFTS). Compiled in
2000-2003, this dataset includes fish tissue samples from 500 randomly
selected lakes and reservoirs across the U.S. Combining data from NLFA
and NFTS, samples from 1633 lake and river sampling sites were selected
for the analysis.
Although the NLFA and NFTS provide rich sources of data on Hg
levels in freshwater fish for the study area, the fish tissue samples
in these databases vary in several respects. For example, they vary
according to the size and species of fish sampled and according to the
sampling method used (e.g., the cut of fish sampled). We limited the
samples we used for this analysis to fish likely to be caught and
consumed, defined for this analysis as fish greater than or equal to
seven inches in length.
The TSD describes in more detail how we used the data available in
the NLFA and NFTS datasets.
E. Air Quality Modeling of the Impacts of Utility Unit Hg on Fish
Tissue Levels
EPA conducted computerized modeling that indicates the effects of
various scenarios for Utility Unit Hg emissions on fish tissue at the
NLFA-NFTS sites across the country, in both a 2001 base case and in
projected control cases for the year 2020. This section summarizes the
emissions inventories used in those modeling scenarios, and the air
quality modeling, that serve as the basis for determining the fish
tissue impacts of Hg from Utility Units at various levels of emissions.
EPA used a sophisticated air quality model to estimate baseline and
post-control annual total Hg deposition for each scenario. EPA then
combined the estimated changes in Hg depositions with fish tissue data
to determine estimated changes in methylmercury levels in fish tissues.
EPA then combined those changes in fish tissue methylmercury levels
with estimates of fish consumption, for use in estimating exposure
levels.
1. Air Quality Modeling for Hg Deposition From Utility Mercury
Emissions
This section summarizes the methods for estimating Hg deposition
for 2001 and 2020 base cases and control scenarios. EPA estimated the
Hg deposition changes using national-scale applications of the
Community Multi-Scale Air Quality (CMAQ) model in the contiguous United
States.
a. CMAQ Model and Hg Deposition Estimates. CMAQ is a three-
dimensional grid-based Eulerian air quality model designed to estimate
annual particulate concentrations and Hg deposition over large spatial
scales (e.g., over the contiguous United States). Because it accounts
for spatial and temporal variations as well as differences in the
reactivity of emissions, CMAQ is useful for evaluating the impacts of
changes in utility Hg emissions, under various scenarios, on U.S. Hg
deposition. Our analysis applies the modeling system to the entire
United States for the following emissions scenarios:
(1) A 2001 base year;
(2) A 2001 base year of utility Hg emissions only;
(3) A 2020 projection that includes utility Hg emissions as reduced
through implementation of CAIR;
(4) A 2020 projection with utility Hg emissions zeroed-out; \46\
---------------------------------------------------------------------------
\46\ The reference to ``zeroed out'' means that the modeled
inventory did not include any amount of Hg emissions from utilities.
This ``zero-out'' technique allows focus on the impact of the
utilities alone.
---------------------------------------------------------------------------
(5) A 2020 projection that includes utility Hg emissions as reduced
through implementation of CAMR (which, in turn, reflects both CAIR
reductions and the reductions from the additional, 2018 controls); and
(6) A 2020 projection that includes utility Hg emissions as reduced
through a second CAMR option (this second CAMR option reflects both
CAIR reductions and a set of additional reductions that are tighter
than the ones adopted in CAMR).
The CMAQ version 4.3 was employed for this CAMR modeling analysis.
This version reflects updates in a number of areas to improve
performance and address comments from the peer review. CMAQ simulates
every hour of every day of the year and, thus, requires a
[[Page 16016]]
variety of input files that contain information pertaining to the
modeling domain and simulation period. These include hourly emissions
estimates and meteorological data in every grid cell, as well as a set
of pollutant concentrations to initialize the model and to specify
concentrations along the modeling domain boundaries. These initial and
boundary concentrations were obtained from output of a global chemistry
model. We use the model predictions in a relative sense by first
determining the ratio of Hg deposition predictions. The calculated
relative change is then combined with the corresponding fish tissue
concentration data to project fish tissue concentrations for the future
case scenarios.
b. Modeling Domain and Simulation Periods. The modeling domain
encompasses the lower 48 States and extends from 126 degrees to 66
degrees west longitude and from 24 degrees north latitude to 52 degrees
north latitude. The modeling domain is segmented into rectangular
blocks referred to as grid cells. The model actually predicts pollutant
concentrations for each of these grid cells. For this application, the
horizontal grid cells are roughly 36 km by 36 km. In addition, the
modeling domain contains 14 vertical layers with the top of the
modeling domain at about 16,200 meters. Within the domain each vertical
layer has 16,576 grid cells.
The simulation periods modeled by CMAQ included separate full-year
application for each of the emissions scenarios modeled.
c. Model Inputs. CMAQ requires a variety of input files that
contain information pertaining to the modeling domain and simulation
period. These include gridded, hourly emissions estimates and
meteorological data and initial and boundary conditions. Separate
emissions inventories were prepared for the 2001 base year and each of
the future-year base cases and control scenarios. All other inputs were
specified for the 2001 base year model application and remained
unchanged for each future-year modeling scenario.
CMAQ requires detailed emissions inventories containing temporally
allocated emissions for each grid cell in the modeling domain for each
species being simulated. The previously described annual emission
inventories were preprocessed into model-ready inputs through the
emissions preprocessing system. Details of the preprocessing of
emissions are provided in the Clean Air Interstate Rule Emissions
Inventory Technical Support Document (Emissions Inventory TSD).
Meteorological inputs reflecting 2001 conditions across the contiguous
United States were derived from version 5 of the Mesoscale Model (MM5).
These inputs include horizontal wind components (i.e., speed and
direction), temperature, moisture, vertical diffusion rates, and
rainfall rates for each grid cell in each vertical layer.
The lateral boundary and initial species concentrations are
provided by a three-dimensional global atmospheric chemistry and
transport model (GEOS-CHEM). The lateral boundary species
concentrations varied with height and time (every 3 hours). Terrain
elevations and land use information were obtained from the U.S.
Geological Survey database at 10 km resolution and aggregated to the
roughly 36 km horizontal resolution used for this CMAQ application.
d. CMAQ Model Evaluation. An operational model performance
evaluation for Hg wet deposition for 2001 was performed to estimate the
ability of the CMAQ modeling system to replicate base-year wet
deposition of Hg. Because measurements for the dry deposition of Hg do
not currently exist, the modeled dry deposition performance could not
be evaluated. The wet deposition evaluation principally comprises
statistical assessments of model versus observed pairs that were paired
in time and space on a weekly basis. This evaluation includes
comparisons of model predictions to the corresponding weekly
measurements from the Mercury Deposition Network (MDN).
As discussed in the TSD, in EPA's view, CMAQ model performance for
wet deposition shows very good agreement with the MDN monitoring sites
with an underprediction bias well within accepted performance criteria.
It should be noted that the application of a sophisticated
photochemical grid model like CMAQ has been demonstrated to be
appropriate to support national and regional assessments of control
strategies on atmospheric concentrations such as today's rule.
Therefore, for purposes of assessing impacts on regional patterns of Hg
deposition, we aggregate individual CMAQ grids to watersheds.
2. Emission Inventories and Estimated EGU (Utility Unit) Emission
Reductions
As discussed in the Clean Air Mercury Rule Emission Inventory
Technical Memorandum, EPA developed 2001 and 2020 Hg emission
inventories for the air quality modeling. EPA relied on the 2001 Hg
emission inventory as the base case. The base case consists of the
level of Hg emissions, including Utility Unit emissions reduced by
controls implemented for purposes of the acid deposition provisions and
for other purposes, before reductions under CAIR (required under CAA
section 110(a)(2)(D)) or CAMR (required under section 111). For
comparison purposes, EPA also conducted an air quality modeling run of
the 2001 Hg emissions inventories with Utility Units' Hg emissions
``zeroed out.'' EPA relied on the Integrated Planning Model (IPM),
discussed below, to develop projections of EGU emissions for 2020. The
2020 utility Hg emission inventories reflect reductions under various
control scenarios.
a. Use of IPM for Estimating Utility Unit Emissions. EPA projected
future Hg emissions from the power generation sector using the IPM. The
EPA uses IPM to analyze the projected impact of environmental policies
on the electric power sector in the 48 contiguous states and the
District of Columbia.
IPM is a multi-regional, dynamic, deterministic linear programming
model of the U.S. electric power sector. The EPA used IPM to project
both the national level and the unit level of Utility Unit Hg emissions
under different control scenarios. The EPA also used IPM to project the
costs of those controls.
As noted elsewhere, the CAIR SO2 and NOX
controls provide the basis for reducing Hg to the CAIR co-benefit
levels in 2010 and 2020. EPA assumed that states would choose to
implement the CAIR-required SO2 and NOX
reductions by controlling Utility Units, and by doing so through the
EPA-administered cap-and-trade program. This assumption is reasonable,
for present purposes, because of the cost-savings associated with the
cap-and-trade program.
EPA used IPM to project the distribution within the utility
industry of the emission controls to comply with CAIR. EPA then was
able to use IPM to project the amount, and geographic distribution, of
Hg emissions that would result from implementation of those CAIR-
required emissions controls. In addition, EPA used IPM to project the
geographic distribution of the additional emissions controls under
section 111, and the associated costs.
In these IPM runs, EPA assumed that states would implement the Hg
requirements through the Hg cap-and-trade program that EPA is
establishing. EPA further assumed that the States would implement the
additional reductions under section 111, beginning in 2010, through the
same cap-and-trade program. The cap-and-trade program is implemented in
two phases, with a cap
[[Page 16017]]
of 38 tons in 2010 (set at the co-benefits reduction under CAIR) and a
lower cap of 15 tons in 2018. EPA modeling of section 111 projects
banking of excess Hg reductions in the 2010 to 2017 timeframe for
compliance with the cap in 2018 and beyond timeframe. Although states
are not required to adopt the EPA-administered trading program, this
program assures that those reductions will be achieved with the least
cost. For that reason, EPA believes it reasonable to assume that States
will adopt the program.
The National Electric Energy Data System (NEEDS) contains the
generation unit records used to construct model plants that represent
existing and planned/committed units in EPA modeling applications of
IPM. The NEEDS includes basic geographic, operating, air emissions
requirements, and other data on all the generation units that are
represented by model plants in EPA's v.2.1.9 update of IPM.
The IPM uses model run years to represent the full planning horizon
being modeled. That is, several years in the planning horizon are
mapped into a representative model run year, enabling IPM to perform
multiple year analyses while keeping the model size manageable.
Although IPM reports results only for model run years, it takes into
account the costs in all years in the planning horizon. In EPA's
v.2.1.9 update of IPM, the years 2008 through 2012 are mapped to run
year 2010, and the years 2013 through 2017 are mapped to run year 2015,
and the years 2018 through 2022 are mapped to 2020.\47\ Model outputs
for 2009 and 2010 are from the 2010 run year. More detail on IPM can be
found in the model documentation in the docket or at http://www.epa.gov/airmarkets/epa-ipm ipm and more discussion of modeled
scenarios can be found in the Regulatory Impact Assessment for CAIR and
CAMR in the docket.
---------------------------------------------------------------------------
\47\ An exception was made to the run year mapping for an IPM
sensitivity run that examined the impact of a NOX Early
Reduction Pool (ERP). In that run the years 2009 through 2012 were
mapped to 2010 and 2008 was mapped to 2008.
---------------------------------------------------------------------------
IPM has been used for evaluating the economic and emission impacts
of environmental policies for over a decade. The model's base case
incorporates title IV of the Clean Air Act (the Acid Rain Program), the
NOX SIP Call, various New Source Review (NSR) settlements,
and several state rules affecting emissions of SO2 and
NOX that were finalized prior to April of 2004. The NSR
settlements include agreements between EPA and certain utilities. IPM
also includes various current and future state programs in Connecticut,
Illinois, Maine, Massachusetts, Minnesota, New Hampshire, North
Carolina, New York, Oregon, Texas, and Wisconsin. IPM includes state
rules that have been finalized and/or approved by a state's legislature
or environmental agency. The base case is used to provide a reference
point to compare environmental policies and assess their impacts and
does not reflect a future scenario that EPA predicts will occur.
EPA's modeling is based on various input assumptions that are
uncertain, particularly assumptions for Hg control technology, future
fuel prices and electricity demand growth. While IPM contains an
assumption of 90% Hg removal for ACI and, for modeling convenience,
does not constrain the timeframe for the availability of technology,
this should not be interpreted as implying any assessment of the
availability of technology. For further discussion of the availability
of Hg technology, see EPA's Office of Research and Development (ORD)
Control of Emissions from Coal-Fired Electric Utility Boilers: An
Update, EPA/Office of Research and Development, March 2005, in CAMR
docket. There may also be technologies available for SO2 and
NOX control that are not accounted for in IPM. Therefore the
technologies that plants may use to comply with this program may not be
accurately projected by IPM in all cases. These and other assumptions
and uncertainties are discussed further in the RIA for CAIR and CAMR in
the docket. More detail on IPM can be found in the model documentation,
which provides additional information on the assumptions discussed here
as well as all other assumptions and inputs to the model (see docket or
http://www.epa.gov/airmarkets/epa-ipm ipm).
b. Emission Estimates. The emission sources and the basis for
current and future-year inventories are listed in Table VI-1. Table VI-
2 summarizes the Hg emissions and the change in the emissions from EGUs
(Utility Units) that we expect to result under the various EGU control
scenarios (under CAIR and CAMR) that we used in modeling deposition
changes.
Table VI--1. Emission Sources and Basis for Current and Future-Year Mercury Inventories
----------------------------------------------------------------------------------------------------------------
Future-year base case
Sector Emissions source 2001 Base year projections
----------------------------------------------------------------------------------------------------------------
EGU.................................. Power industry electric 1999 National Emission Integrated Planning
generating units Inventory (NEI) data. Model (IPM).
(EGUs).
Non-EGU point sources................ Non-Utility Point...... 1999 NEI, with medical (1) Department of
waste incinerator Energy (DOE) fuel use
sources replaced with projections, (2)
draft 2002 NEI. Regional Economic
Model, Inc. (REMI)
Policy Insight[supreg]
model, (3) decreases
to REMI results based
on trade associations,
Bureau of Labor
Statistics (BLS)
projections and Bureau
of Economic Analysis
(BEA) historical
growth from 1987 to
2002, (4) Maximum
Achievable Control
Technology category
growth and control
assumptions.
Non-point............................ All other stationary 1999 NEI, with medical Same as above.
sources inventoried at waste incinerator
the county level. sources replaced with
draft 2002 NEI.
----------------------------------------------------------------------------------------------------------------
This table documents only the sources of data for the U.S. inventory. The sources of data used for Canada and
Mexico are explained in the technical support memorandum and were held constant from the base year to the
future years.
[[Page 16018]]
Table VI--2. Summary of Modeled Mercury Emissions for Clean Air Mercury Rule
----------------------------------------------------------------------------------------------------------------
Reactive gaseous Particulate
Elemental mercury mercury mercury Total mercury
----------------------------------------------------------------------------------------------------------------
2001 Base Case Emissions (tons)
----------------------------------------------------------------------------------------------------------------
EGU Sources......................... 26.26 20.58 1.73 48.57
Non-EGU Point Sources............... 37.85 13.33 7.60 58.78
Area Sources........................ 5.05 1.53 0.96 7.54
--------------------
All Sources..................... 69.16 35.44 10.29 114.89
-------------------------------------
2001 Utility Mercury Emissions Zero-Out (tons)
----------------------------------------------------------------------------------------------------------------
EGU Sources......................... 0.00 0.00 0.00 0.00
Non-EGU Point Sources............... 37.85 13.33 7.60 58.78
Area Sources........................ 5.05 1.53 0.96 7.54
--------------------
All Sources..................... 42.90 14.86 8.56 66.32
-------------------------------------
2020 With CAIR Emissions (tons)
----------------------------------------------------------------------------------------------------------------
EGU Sources......................... 25.72 7.87 0.83 34.42
Non-EGU Point Sources............... 28.03 10.37 6.61 45.01
Area Sources........................ 5.69 1.30 0.77 7.76
--------------------
All Sources......................... 59.44 19.54 8.21 87.19
-------------------------------------
2020 With CAIR Utility Mercury Emissions Zero-Out
----------------------------------------------------------------------------------------------------------------
EGU Sources......................... 0.00 0.00 0.00 0.00
Non-EGU Point Sources............... 28.03 10.37 6.61 45.01
Area Sources........................ 5.69 1.30 0.77 7.76
--------------------
All Sources..................... 33.72 11.67 7.38 52.77
-------------------------------------
2020 With CAIR and CAMR
----------------------------------------------------------------------------------------------------------------
EGU Sources......................... 17.65 6.57 0.83 25.05
Non-EGU Point Sources............... 28.03 10.37 6.61 45.01
Area Sources........................ 5.69 1.30 0.77 7.76
--------------------
All Sources..................... 51.37 18.24 8.21 77.82
-------------------------------------
2020 With CAIR and Alternative CAMR Control Option
----------------------------------------------------------------------------------------------------------------
EGU Sources......................... 14.33 5.71 0.79 20.83
Non-EGU Point Sources............... 28.03 10.37 6.61 45.01
Area Sources........................ 5.69 1.30 0.77 7.76
--------------------
All Sources..................... 48.05 17.38 8.17 73.60
----------------------------------------------------------------------------------------------------------------
(Note: ``Reactive Gaseous Mercury'' refers to oxidized mercury).
(Note: Table IV-2 includes projections for all EGUs, including
other fossil-fired units, and coal-fired units that are less than 25
MW.)
c. Projected Hg Emissions. Table VI-3 provides projected total Hg
emissions levels in 2010, 2015, and 2020. Because of the banking of
excess emissions reductions under the first phase of the Hg program,
emissions in the second phase will be initially higher than the caps
that are required under CAMR.
Table VI--3. Projected Emissions of Hg with the Base Case \a\ (No
Further Controls), With CAIR, and With Section 111 Controls
[Tons]
------------------------------------------------------------------------
2010 2015 2020
------------------------------------------------------------------------
Base Case........................ 46.6 45.0 46.2
CAIR............................. 38.0 34.4 34.0
CAMR............................. 31.3 27.9 24.3
Alternative CAMR Control Option.. 30.9 25.7 20.1
------------------------------------------------------------------------
\a\ Base case includes Title IV Acid Rain Program, NOX SIP Call, and
state rules finalized before March 2004.
Source: Integrated Planning Model run by EPA.
[[Page 16019]]
Emissions projections are presented for affected coal-fired units.
(Note: Table VI-3 includes projections for all affected units,
i.e., coal-fired units greater than 25 MW.)
3. Effect of Reductions in Utility Unit Hg Emissions on Regional
Patterns of Mercury Deposition and Fish Tissue Methylmercury
Concentrations
EPA uses CMAQ to predict the effect of the various control
scenarios on Hg deposition attributable to Utility Units within the 48
contiguous states. By averaging the 36 km CMAQ gridded deposition
estimates to the watershed (i.e., HUC-8) level, EPA is able to estimate
the effectiveness of reductions in utility Hg emissions in achieving
reductions in deposition attributable solely to Utility Units. In
addition, by comparing changes in Hg deposition before and after
implementation of rule requirements at the geographic location of the
fish tissue sample points, EPA is able to estimate the effect of
reductions in Hg deposition on fish tissue methylmercury concentrations
at the sample points.
EPA generates these changes in Hg deposition by comparing two air
modeling scenarios (e.g., a control scenario versus a baseline scenario
for a particular simulation year). EPA then translates these changes in
Hg deposition into changes in methylmercury fish tissue concentrations
based on a proportionality assumption: i.e., an incremental percent
change in deposition produces a matching percentage change in Hg fish
tissue concentrations.\48\
---------------------------------------------------------------------------
\48\ US EPA, 2001. Mercury Maps: A Quantitative Spatial Link
Between Air Deposition and Fish Tissue: Peer Reviewed Final Report.
EPA-823-R-01-009. Mercury Maps is discussed at length in the TSD.
---------------------------------------------------------------------------
EPA is able to use these modeled changes in methylmercury fish
tissue concentrations, together with information about fish
consumption, to predict changes in population-level Hg exposure. These
exposure changes reveal the extent to which reductions in Utility Unit
Hg emissions, and the extent to which remaining Utility Unit Hg
emissions, affect public health.
F. Fish Tissue Levels of Methylmercury Modeled To Result After
Implementation of CAIR and CAMR
This section describes the amounts of Utility Unit attributable Hg
deposition onto watersheds (termed HUC), as well as the Utility-
attributable methylmercury in fish tissue, all under the various
control scenarios modeled.
1. Utility-Attributable Hg Deposition Patterns
The air quality modeling shows that total Hg deposition is not
highly impacted by utility deposition. The small size of this impact is
evident when utility emissions are, in effect, zeroed out in the 2001
base case. The following tables summarize impacts on total Hg
deposition and Hg deposition attributable to Utility Units.
Table VI-4.--Summary Statistics for Total Hg Deposition
[Aggregated to the HUC-8 level]
--------------------------------------------------------------------------------------------------------------------------------------------------------
2001 Utility 2020 Base case 2020 Utility 2020 CAMR 2020 CAMR
2001 Base case zero out (with CAIR) zero out requirements alternative
--------------------------------------------------------------------------------------------------------------------------------------------------------
Minimum................................................. 6.94 6.94 6.08 5.90 6.08 6.07
Maximum................................................. 54.54 54.38 62.76 62.72 62.76 62.75
50th percentile......................................... 15.92 14.60 14.59 13.92 14.44 14.39
90th percentile......................................... 22.16 19.48 19.46 19.04 19.37 19.33
99th percentile......................................... 32.35 27.20 29.15 28.93 28.96 28.95
--------------------------------------------------------------------------------------------------------------------------------------------------------
(All units are expressed in micrograms per square meters.)
Table VI-5. Summary Statistics for Utility Attributable Hg Deposition
[aggregated to the HUC-8 level]
----------------------------------------------------------------------------------------------------------------
2020 Base case 2020 CAMR 2020 CAMR
2001 Base case (with CAMR) Requirements Alternative
----------------------------------------------------------------------------------------------------------------
Minimum......................................... 0.00 0.00 0.00 0.00
Maximum......................................... 19.71 4.03 3.85 3.80
50th percentile................................. 0.39 0.3 10.26 0.22
90th percentile................................. 4.08 1.38 1.16 0.99
99th percentile................................. 10.15 2.56 2.17 2.04
----------------------------------------------------------------------------------------------------------------
(All units are expressed in micrograms per square meters.)
The median deposition level is reduced by only 8 percent when
utilities emissions are zeroed out in 2001, suggesting that utilities
are not a major source of Hg deposition in most HUCs. Even so, at HUCs
with the highest deposition levels, zeroing out utilities reduces the
99th percentile deposition level by 16 percent, suggesting that there
are relatively larger impacts of utilities in high deposition areas.
By 2020, after implementation of CAIR, significant reductions in
deposition attributable to utilities occurs. HUCs with high levels of
utility deposition receive a larger reduction in Utility-attributable
Hg deposition relative to HUCs with a relatively small level of
Utility-attributable deposition. Specifically, CAIR results in a 75
percent reduction in the 99th percentile of Utility-attributable
deposition, and a 20 percent reduction in the 50th percentile. CAIR
also shifts the distribution of utility-attributable deposition. In the
2001 base case, 10 percent of HUCs had greater than 20 percent of
deposition attributable to utilities. In the 2020 post-CAIR base case,
no HUCs had greater than 20 percent of deposition attributable to
utilities, and 90 percent had less than 9 percent of deposition
attributable to utilities.
[[Page 16020]]
Additional reductions in Hg emissions due to the CAMR requirements
result in relatively small additional shifts in the distribution of
deposition. Additional emissions reductions due to the CAMR
requirements result in a small additional reduction in the number of
HUCs with a high percentage of utility-attributable emissions. (The
incremental impact of the CAMR alternative relative to the promulgated
CAMR requirements is very small.)
2. EGU-Attributable Methylmercury Fish Tissue Levels
The following tables summarize the methylmercury fish tissue levels
associated with the various Utility Unit Hg emissions scenarios. All
units refer to mg (of methylmercury) per kg (fish tissue), or parts per
million (ppm). As a frame of reference, it should be noted that EPA's
default water quality criterion is 0.3 mg/kg.
Table VI--6. Summary Statistics for Total Fish Tissue Methylmercury
[Sample locations]
--------------------------------------------------------------------------------------------------------------------------------------------------------
2001 Utility 2020 Base case 2020 CAMR 2020 CAMR
2001 Base case zero out CAIR 2020 Zero out requirements alternative
--------------------------------------------------------------------------------------------------------------------------------------------------------
Minimum................................................. 0.00 0.00 0.00 0.00 0.00 0.00
Maximum................................................. 4.49 3.64 3.65 3.46 3.63 3.61
50th percentile......................................... 0.25 0.21 0.21 0.20 0.21 0.21
90th percentile......................................... 0.90 0.81 0.79 0.77 0.79 0.78
99th percentile......................................... 1.80 1.65 1.64 1.57 1.63 1.63
--------------------------------------------------------------------------------------------------------------------------------------------------------
(All units are in mg methylmercury per kg fish tissue.)
Table VI--7. Summary Statistics for Utility Attributable Fish Tissue Methylmercury
[Across sampling locations]
----------------------------------------------------------------------------------------------------------------
2020 (with 2020 CAMR 2020 CAMR
2001 Base CAIR) Requirements Alternative
----------------------------------------------------------------------------------------------------------------
Minimum......................................... 0.00 0.00 0.00 0.00
Maximum......................................... 0.85 0.25 0.19 0.18
50th percentile................................. 0.03 0.01 0.01 0.01
90th percentile................................. 0.11 0.03 0.03 0.03
99th percentile................................. 0.26 0.10 0.09 0.08
----------------------------------------------------------------------------------------------------------------
(All units are in mg methylmercury per kg fish tissue.)
a. 2001 Base case and 2001 Utility Zero-out. In the 2001 base case,
as a result of all international and U.S. emissions, and before U.S.
utilities implement reductions from CAIR or CAMR, the 50th percentile
of the sample points had an estimated methylmercury fish tissue
concentration of 0.25 mg/kg. The 90th percentile water body had an
estimated methylmercury fish tissue concentration of 0.90 mg/kg, and
the 99th percentile had 1.80 mg/kg.
The amount of methylmercury attributable solely to utilities in the
2001 base case, which becomes evident when utilities are zeroed out, is
of course much smaller. The 50th percentile of the sample points had an
estimated methylmercury fish tissue concentration. attributable solely
to utilities, of 0.03 mg/kg. The 90th percentile had 0.11 mg/kg, the
99th percentile had 0.26 mg/kg, and the maximum individual sample point
had 0.85 mg/kg.
It should be recalled that EPA recommends the water quality
criterion of 0.3 mg/kg as a level that, given fish consumption at the
90th percentile level, would result in exposure levels below the RfD.
For present purposes, EPA does not consider the water quality criterion
of 0.3 mg/kg as a bright-line test for evaluating fish tissue
methylmercury levels attributable to U.S. Utility Units. Rather, the
criterion serves as establishing a broad frame of reference, that
serves to place into context both the overall methylmercury fish tissue
levels (which are attributable to methylmercury from all sources) and
the methylmercury levels attributable to Utility Units.
These results indicate the relatively small percentage of U.S.
utility contribution to U.S. fish tissue methylmercury levels.
b. 2020: Utilities With CAIR Reductions. EPA's modeling shows that
in 2020, as a result of all international and U.S. emissions, and with
U.S. utilities implementing reductions from CAIR (but not CAMR), the
50th percentile of the sample points is projected to have a
methylmercury fish tissue concentration of 0.21 mg/kg. The 90th
percentile is projected to have 0.79 mg/kg, and the 99th percentile is
projected to have 1.64 mg/kg.
The amount of methylmercury in fish attributable solely to
utilities in 2020, after implementation of the CAIR reductions (but,
again, before CAMR), of course is smaller. The 50th percentile of the
sample points is projected to have fish tissue concentration,
attributable solely to utilities of 0.01 mg/kg. The 90th percentile is
projected to have 0.03 mg/kg, the 99th percentile is projected to have
0.10 mg/kg, and the maximum individual sample point (i.e., the one with
the highest methylmercury levels) is projected to have 0.25 mg/kg.
Again, using the 0.3 mg/kg methylmercury water quality criterion as
a broad frame of reference serving to place in context both the overall
methylmercury fish tissue levels (attributable to methylmercury from
all sources) and the methylmercury fish tissue levels attributable to
Utility Units, it is clear that the latter levels, following
implementation of CAIR, are low.
c. 2020: Utilities with CAMR Controls. The CAMR level of controls
achieve further, albeit small, reductions in methylmercury fish tissue
concentrations. Compared to the CAIR controls, the CAMR controls would
further reduce, in 2020, methylmercury fish tissue concentrations by,
in the 99th percentile, 0.01 mg/kg.
d. 2020: Utilities with Alternative CAMR Controls. EPA evaluated,
but did not adopt, a slightly tighter level of CAMR controls. These
alternative
[[Page 16021]]
CAMR controls would have achieved still further, albeit, again small,
reductions in Hg deposition and in fish tissue methylmercury levels.
Compared to the CAIR controls, these alternative CAMR controls would
reduce methylmercury fish tissue levels in 2020 by, in the 99th
percentile, 0.02 mg/kg.\49\
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\49\ A detailed discussion of the control alternatives we
considered and the reason for our final selection is contained in
the preamble to the final CAMR.
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5. Overall Impact of CAIR and CAMR Controls on Utility Unit Hg
Emissions
As described in the CAIR rule, CAIR reduces EGU Hg emissions from
pre-CAIR levels by a substantial percentage. CAMR reduces Utility Unit
Hg emissions, from CAIR levels, by 27 percent. CAMR reduces ionic Hg
emissions, those that are most likely to result in local and regional
deposition, by 17 percent relative to CAIR levels.
These reductions tend to occur from the largest sources. That is,
the larger the source of Hg emissions, the more likely it is to
implement CAIR or CAMR controls, and therefore the more likely it is to
reduce its Hg emissions. More specifically, under the cap-and-trade
system, the marketplace tends to direct controls to the largest
emitters because those emitters can achieve the most cost-effective
reductions. Compared to smaller emitters, these larger emitters have an
incentive to implement more stringent controls, thereby reducing their
emissions further below the level of their allowances, and thereby
generating a larger number of allowances for sale to defray control
costs. See ``Proposed National Emissions Standards for Hazardous Air
Pollutants; and in the Alternative, Proposed Standards of Performance
for New and Existing Sources: Electric Utility Steam Generating
Units,'' 9 FR 4652, 4702-03 (Jan. 30, 2004).
G. Exposure to Utility-Attributable Methylmercury Levels in Fish Tissue
CAIR reduces median Utility-attributable fish tissue methylmercury
levels, from pre-CAIR levels, by 67 percent. CAIR reduces the 99th
percentile Utility-attributable fish tissue methylmercury levels, from
pre-CAIR levels, by 60 percent. CAMR reduces median Utility-
attributable fish tissue methylmercury levels, from CAIR levels, by 12
percent. CAMR reduces the 99th percentile Utility-attributable fish
tissue methylmercury levels, from CAIR levels, by 9 percent.
As a result of these reductions, after CAIR or CAMR, no sample site
remains in which Utility-attributable, emissions cause methylmercury
fish tissue levels to exceed 0.3 mg/kg (EPA's water quality criterion).
Even with these reductions, although the levels of methylmercury in
fish tissues attributable to Utility Units are small, the magnitude of
methylmercury exposure depends on consumption levels and the
sensitivity of the individual. For purposes of assessing whether
utility Hg emissions are reasonably anticipated to result in hazards to
public health, we focused on evaluating utility attributable
methylmercury exposures for women of childbearing age in the general
U.S. population who consume non-commercial (e.g., recreational)
freshwater fish in U.S. waterbodies.
This section describes available information as to the consumption
levels of women of child-bearing age within the population of
recreational fishers who consume at typical levels, and within high-
consumption sub-populations; and discusses the amounts of methylmercury
that may be ingested as a result of those consumption levels.
1. General Population
We believe that only those women of childbearing age who consume
noncommercially caught U.S. freshwater fish have the potential for
significant exposures to utility-attributable methylmercury. As a
result, our assessment of the hazards to public health focuses on those
women.
2. Recreational Fishers Who Consume Fish At Typical Levels.
a. Consumption Levels. For our analysis of recreational freshwater
fish consumption, EPA has determined that the sport-caught fish
consumption rates for recreational freshwater fishers specified as
``recommended'' in the EPA's Exposure Factors Handbook (mean of 8 gm/
day and 95th percentile of 25 gm/day), represent the most appropriate
values for present purposes. These recommended values were derived
based on ingestion rates from four studies conducted in Maine,
Michigan, and Lake Ontario (Ebert et al., 1992; Connelly et al., 1996;
West et al., 1989; West et al., 1993). These studies are suitable
because they included information for annual-averaged daily intake
rates for self-caught freshwater fish by all recreational fishers
including consumers and non-consumers. The mean values presented in
these four studies ranged from 5 to 17 gm/day, while the 95th
percentile values ranged from 13 to 39 gm/day.\50\
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\50\ The 39 gm/day value actually represents a 96th percentile
value.
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The EPA ``recommended values'' were developed by considering the
range and spread of means and 95th percent values presented in the four
studies. EPA recognizes that use of mean and 95th percentile
consumption rates based on these four studies may not be representative
of fishing behavior in every state and that there may be regional
trends in consumption that differ from the values used in this
analysis. However, EPA believes that these four studies represent the
best available data for developing recreational fisher ingestion rates
for present purposes.
As a result, for today's purposes of evaluating the potential for
health effects for consumers of recreational freshwater fish resulting
from exposure to utility-attributable methylmercury, we consider both
the mean of 8 gm/day consumption and the 95th percentile amount of 25
gm/day.
b. Levels of Consumption Combined with Levels of Utility-
Attributable Methylmercury in Fish Tissue. As described above, fish
tissue levels of Utility-attributable methylmercury, for virtually all
sample points, are only a fraction of the 0.3 mg/kg (fish tissue) water
quality criterion. EPA evaluated recreational fish consumers' exposure
to this Utility-Attributable methylmercury by calculating the level of
exposure to this methylmercury and comparing it to the RfD when
background exposures are not considered. For the purposes of assessing
population exposure due solely to power plants, we create an index of
daily intake (IDI).The IDI is defined as the ratio of exposure due
solely to power plants to an exposure of 0.1 [mu]ug/kg bw/day. The IDI
is defined so that an IDI of 1 is equal to an incremental exposure
equal to the RfD level, recognizing that the RfD is an absolute level,
while the IDI is based on incremental exposure without regard to
absolute levels. Note that an IDI value of 1 would represent an
absolute exposure greater than the RfD when background exposures are
considered.
At either the mean fish consumption rate of 8 gm/day or the 95th
percentile fish consumption rate of 25 gm/day for recreational fish
consumers discussed above, and using the 99th percentile methylmercury
fish tissue concentration attributable to Utility Unit (and a typical
body weight of 64 kg for women of child-bearing age), the calculated
Utility-attributable methylmercury exposures are 0.013 [mu]ug/kg body
weight per day and 0.04 [mu]ug/kg body weight per day, respectively.
Both calculated exposures are well below the RfD of 0.1 [mu]ug/kg body
weight per day (an IDI value well below 1).
[[Page 16022]]
EPA uses the RfD to place ingestion levels in context. The RfD
level of methylmercury ingestion--0.1 [mu]ug/kg body weight--should not
be considered a bright line standard above which adverse health effects
occur, but rather as an aid in establishing the context for evaluating
both overall methylmercury ingestion (arising from methylmercury from
all sources) as well as Utility-Attributable methylmercury ingestion in
light of consumption rates. Our analysis concludes that Utility Unit Hg
emissions do not cause hazards to the health of the general public or
higher fish consuming recreational anglers.
3. High-Level Fish Consumption Sub-Populations
Although exposure to Utility-attributable methylmercury from
freshwater fish tissue is quite low for recreational fishers generally,
as just described, EPA recognizes that certain sub-populations consume
higher levels of U.S. freshwater fish. These populations may include a
subset of recreational fishers who consume large quantities of fish,
individuals who are subsistence fishers, and individuals who are part
of certain ethnic groups. EPA is aware that at very high consumption
levels, even relatively small concentrations of methylmercury in fish
may result in exposures that exceed the RfD.
However, as described in the TSD, characterization of fish
consumption rates for the highest fish consuming subpopulations (e.g.,
Native American and other ethnic populations exhibiting subsistence-
like consumption) in the context of a larger regional or national
analysis is technically challenging. Peer reviewed study data on these
populations is relatively limited, especially when subjected to the
criteria outlined in the TSD. Many of the high consumption groups that
have been studied are located near the ocean and consequently have a
significant fraction of their overall exposure comprised of saltwater
fish. In addition, some of these studies provide details on seasonal
consumption rates, but do not integrate these rates to provide an
overall mean annual-averaged consumption rate relevant to an RfD-based
analysis.
Although many of these studies provide mean consumption rates, few
have identified specific high-end percentile values (e.g., 90th, 95th
or 99th percentile consumption rates). Instead, many studies, including
a number of non-peer reviewed sources, cite non-specific high-end or
bounding point estimates (e.g., the range of consumption rates for the
Ojibwe submitted for the CAMR NODA). While these point values can be
used in developing high-end bounding scenarios for evaluating risk to
these groups, they do not support population-level analysis of exposure
since they cannot be used to fit distributions characterizing
variability in fish consumption rates across these sub-populations (as
noted above, modeling of population-level exposures requires that
distributions characterizing fish consumption rates across a particular
population be developed).
An additional challenge in characterizing high-level fish
consumption is that care needs to be taken in extrapolating study
results from one group to another. This reflects the fact that high-
level fish consumption is often tied to socio-cultural practices and
consequently consumption rates for a study population cannot be easily
transferred to other groups which may have different practices (e.g.,
practices for one Native American tribe may not be relevant to another
and consequently behavior regarding fish consumption may not be
generalized).
Despite these challenges in characterizing high-level consumption,
EPA has developed recommended subsistence-level fish consumption rates
of 60 g/day (mean) and 170 g/day (95th percentile) (EPA, 1997, Exposure
Factors Handbook). These values are based on a study of several Native
American Tribes located along the Columbia River in Washington State.
Although these consumption rates are specific to the tribes included in
the study and reflect their particular socio-cultural practices
(including seasonality and target fish species), EPA believes that this
study does provide a reasonable characterization of high-consuming
subsistence-like freshwater fishing behavior (EPA, 1997, Exposure
Factors Handbook). Therefore, in the absence of data on local
practices, EPA recommends that these consumption rates be used to model
high-consuming groups in other locations. It is important to note that,
as explained above, application of these subsistence consumption rates
outside of the original Columbia River study area could be problematic
because it would be difficult to transfer these consumption rates to a
different group that might exhibit different fishing behavior. However,
these recommended rates can be used to model subsistence scenarios at
different locations.
Although these subsistence consumption rates are recommended by
EPA, commenters (including NODA comments obtained for this rule), have
identified alternative consumption rates for specific high consuming
groups that are in some instances, higher than these recommended
values. For example, a survey by the Great Lakes Indian Fish and
Wildlife Commission (GLIFWC) (as referenced in comments to the CAMR
NODA) indicates that consumption rates by members of Ojibwe Great Lakes
tribes during fall spearing season may range from 155.8-240.7 g/day and
may range from 189.6-292.8 g/day during the spring. EPA has reviewed
these comments and does not believe that it would be appropriate to
rely on them for purposes this rulemaking. First, the data has not been
peer reviewed. Moreover, it is not clear from the comments how many
people consume fish at those rates, to what extent those fish consumers
are women of child-bearing years, and how to annualize these seasonal
sales.\51\
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\51\ As discussed below, the Ojibwe Great Lakes tribes do not
appear to be located in areas with high utility-attributable Hg
deposition.
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For all the above reasons, and despite comments indicating that
some subgroups may have larger short-term consumption rates, EPA
believes that the Columbia River-based consumption rates of between 60
g/day (mean) and 170 g/day (95th percentile) are appropriate default
values for subsistence fish consumers.
H. EPA Concludes That Utility Hg Emissions Remaining After Imposition
of Other Requirements of the Act, in Particular CAA Sections
110(a)(2)(D) and 111, Do Not Result in Hazards to Public Health
As discussed above, Congress mandated that EPA assess hazards to
public health reasonably anticipated to occur as a result of utility
HAP emissions remaining after imposition of the requirements of the
Act, and to regulate Utility Units under section 112 if EPA determines
that such regulation is ``appropriate'' and ``necessary.'' The issue of
whether the level of Hg emissions from Utility Units remaining after
implementation of CAA section 110(a)(2)(D), and independently section
111, cause hazards to public health is directly relevant to our
conclusion set forth in section IV.A. above, namely, that it is not
appropriate to regulate coal-fired Utility Units under section 112 on
the basis of Hg emissions. For the reasons discussed below, EPA
concludes that the level of Hg emissions remaining after implementation
of CAIR, and, independently, CAMR, which implement sections
110(a)(2)(D) and 111, respectively, do not result in hazards to public
health.
1. ``Hazards to Public Health'' Under Section 112(n)(1)(A)
[[Page 16023]]
Section 112(n)(1)(A) establishes the backdrop against which our
utility ``appropriate and necessary'' determination should be judged.
Again, we must decide whether we reasonably anticipate utility Hg
emissions remaining after imposition of the requirements of the Act to
cause hazards to public health. If they do, then we must determine
whether it is appropriate and necessary to regulate Utility Units under
section 112. If utility Hg emissions do not cause public health
hazards, however, which indeed is what we conclude today, then it is
not appropriate to regulate such emissions under section 112, and there
is no need to proceed to the ``necessary'' prong of the section
112(n)(1)(A) inquiry, as explained above.
Section 112(n)(1)(A) defines neither what constitutes a ``hazard''
to public health nor what EPA's obligations would be if such hazard
were identified. Therefore, we believe that EPA has wide discretion,
using its technical expertise, to define ``hazards to public health,''
and to determine whether Hg emissions from utilities pose such a
hazard. EPA's judgment should only be overturned if it is deemed
unreasonable, not merely because other, reasonable alternatives exist.
Department of Treasury v. FLRA, 494 U.S. 922, 933 (1990); Texas Office
of Public Utility Counsel v. FCC, 265 F.3d 313, 320 (5th Cir. 2001).
Although section 112(n)(1)(A) does not define ``hazards to public
health,'' section 112(n)(1)(C) offers guidance with respect to
determining whether Hg emissions result in hazards to public health. In
that section, Congress asked the National Institute of Environmental
Health Sciences to conduct a study to determine the ``threshold level
of mercury exposure below which adverse human health effects are not
expected to occur.'' (Emphasis added) Congress further mandated that
the study include a threshold for Hg concentrations in fish tissue
which may be consumed, including consumption by ``sensitive
populations'' without adverse effects on public health. Implicit in
this direction, is that Congress was concerned, first about public
health, not environmental effects. EPA has identified the exposure to
Hg through consumption of contaminated fish as a pathway to human
health effects, and EPA has also, in its discretion, looked at the
health effects on sensitive populations.
In interpreting what ``hazards to public health'' might be
reasonably anticipated under section 112(n)(1)(A), we think it is also
useful to look at the DC Circuit's Vinyl Chloride decision, 824 F.2d
1146 (1987), and the analysis EPA articulated in its so-called
``benzene'' analysis, 54 FR 38044 (Sept. 14, 1989). Although the Vinyl
Chloride decision and ``benzene'' analysis address the issue of how to
protect public health ``with an ample margin of safety,'' and are thus
more stringent than the standard established in section 112(n)(1)(A),
we nevertheless believe that the general principles articulated in
Vinyl Chloride and the ``benzene'' analysis are relevant to our
analysis of assessing hazards to public health pursuant to section
112(n)(1)(A). Some of those key principles include: (1) ``Safe'' does
not mean ``risk free,'' (Administrator is to determine what risks are
acceptable in the world in which we live, where such activities as
driving a car are considered generally safe notwithstanding the known
risk involved), Vinyl Chloride, 824 F.2d at 1165; (2) something is ``
`unsafe' only when it threatens humans with a significant risk of
harm,' '' id. at 1153; (3) EPA, not the courts, has the technical
expertise to determine what risks are acceptable, id. at 1163; (4) EPA
is permitted to account for uncertainty and to use ``expert discretion
to determine what action should be taken in light of that
uncertainty,'' id.; and (5) in determining what is ``safe'' or
``acceptable,'' EPA should consider a variety of factors, including:
(a) Estimated risk to a maximally exposed individual (the so-called
``maximum individual risk'' or ``MIR''); (b) overall incidence of
cancer or other serious health effects within the exposed population;
(c) the numbers of persons exposed within each individual lifetime risk
range; (d) the science policy assumptions and uncertainties associated
with the risk measures; (e) weight of the scientific evidence for human
health effects; and (f) other quantified or unquantified health
effects. (See 54 FR at 38045-46, 38057).
In assessing whether remaining utility HAP emissions pose hazards
to public health, consistent with section 112(n)(1)(C) and the above
identified factors, we looked at the public's, including sensitive
populations' (i.e., fish consumers), exposure to methylmercury through
fish consumption attributable to utilities alone. Based on this
assessment, and as explained further below, EPA concludes that
remaining utility HAP emissions do not pose hazards to public health.
2. CAIR and CAMR Reduce the Public's Methylmercury Exposure Due to Fish
Consumption to Below the Methylmercury RfD (Below an IDI Value of 1)
As discussed above, EPA has adopted a water quality criterion for
methylmercury for states to use in establishing water quality standards
to protect public health. The criterion, expressed as a fish tissue
concentration, of 0.3 mg/kg was derived from the methylmercury RfD
(taking into account the possibility that a person may be exposed to
methylmercury via commercial fish to some degree, as expressed in the
RSC described elsewhere). At this level, people consuming at a high-end
fish consumption rate of 17.5 grams per day would not be exposed above
the methylmercury RfD. As noted above, this value represents the 90th
percentile fish consumption rate.
In the base year of 2001 (i.e., prior to both CAIR and CAMR), fish-
tissue methylmercury concentrations at the 90th percentile, 99th
percentile, and maximum (that is, the single highest concentration)
levels, attributable to utilities, are 0.11, 0.27, and 0.85 mg/kg,
respectively. CAIR reduces the utility-attributable methylmercury fish-
tissue concentrations at the 90th percentile, 99th percentile, and
maximum level to 0.03, 0.10, and 0.25 mg/kg, respectively. CAMR reduces
these concentrations even further to 0.03, 0.09, and 0.19 mg/kg,
respectively. These post CAIR and CAMR levels are considerably below
the methylmercury water quality criterion of 0.3 mg/kg.
At all of these post-control methylmercury levels, fish consumers
at the water quality criterion 90th percentile consumption level of
17.5 grams per day are well below the RfD (below an IDI value of 1).
Further, these concentration values when applied to the 95th percentile
consumption rate for recreational freshwater anglers identified in
EPA's Exposure Factors Handbook, i.e., 25 grams per day, also result in
exposures below the RfD (below an IDI value of 1). As a result, it is
evident that the general population (which is expected to consume less
U.S. freshwater fish than recreational anglers) does not confront
hazards to public health from utility-attributable methylmercury.
At the methylmercury fish tissue concentrations attributable to
utilities remaining after implementation of CAIR and CAMR, it is
possible that consumers eating at the subsistence-level fish
consumption rates of 60 g/day (mean) and 170 g/day (95th percentile),
see Exposure Factors Handbook, could exceed the RfD (an IDI value
greater than 1) as a result of utility-attributable emissions if they
are in fact consuming fish from the most contaminated locations. In
other words, for a fish consumer to exceed the RfD (an IDI value
greater than 1) as a result of utility
[[Page 16024]]
Hg emissions, they have to both (1) consume fish at the highest
consumption rates and (2) consume fish from waterbodies with the
highest levels of utility-attributable Hg fish-tissue concentrations.
As discussed in the TSD, the probability of these factors converging is
quite low. For example, after CAIR, the probability that a recreational
angler will exceed the RfD (an IDI value greater than 1) exclusively as
a result of utility Hg emissions is only 0.01 percent. After CAMR, the
probability drops even lower. Our analysis further shows that even if
there were a convergence of the unlikely factors of consuming at the
99th percentile consumption rates and at the 99th percentile
methylmecury fish tissue concentrations, exposure would exceed the RfD
by only 10 percent (an IDI value of 1.1). Exceeding the RfD by this
amount (an IDI value of 1.1) does not mean that an adverse effect will
occur. Indeed, 10 percent above the RfD (an IDI value of 1.1), or 0.11
[mu]g/kg-bw/day, is below the World Health Organization's level of 0.23
[mu]g/kg-bw/day.\52\
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\52\ The choice of an ``acceptable'' risk level is one of policy
informed by science. The RfD does not represent a ``bright line''
above which individuals are at risk of significant adverse effects.
Rather, it reflects a level where EPA can state with reasonable
certainty that risks are not appreciable. The Agency further notes
that a number of other national and international scientific bodies
have assessed the health effects of Hg and have adopted levels
greater than EPA's RfD. As exposure levels increase beyond the RfD,
the possibility of deleterious effects increases, but the point at
which they become ``unacceptable'' must be determined on a case-by-
case basis. In making this determination, the Agency considers a
number of factors including: (1) Confidence in the risk estimate:
How certain is the scientific information supporting the link
between possible health effects and exposures?; (2) the effects of
concern: How serious are the health effects?; (3) the size of the
population at risk, as well as the distribution of risk within the
population. The Agency has considered these factors in the case of
Hg and has concluded that the exposures above the IDI described
elsewhere in this chapter do not constitute an unacceptable risk.
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Consumption rates for subsistence fishers are much higher than
recreational anglers. As such, these populations have a greater
probability of exceeding the RfD (an IDI value greater than 1). For
this to happen, the subsistence fisher still must be at the high-end of
the distribution for both consumption and utility-attributable
methylmercury fish tissue concentrations. Our statistical data suggest
that subsistence anglers at the 99th percentile consumption rate and
the 99th percentile concentration level could exceed the RfD (an IDI
value greater than 1). Holding consumption rates at the 99th
percentile, the subsistence angler will likely exceed the RfD (an IDI
value greater than 1) at or above the 72nd percentile fish tissue
concentration.
Again, the likelihood of this occurring is very small. Specific
data on concentrations in fish at waterbodies frequented by subsistence
fishing populations has not been generated. To get a sense of tribal
location in relation to utility-attributable Hg deposition post-CAIR,
we overlaid the 2000 Census data on the location of Native American
populations (by census tract) on our CMAQ models. Visual inspection of
the resulting map shows that the overwhelming majority of tribal
populations live outside of areas most impacted by utility-attributable
Hg deposition. See TSD. This suggests that the 99th percentile of the
utility attributable methylmercury concentrations is likely
inappropriate as an upper bound for Native American exposures, further
reducing the probability that, post CAIR, and even more so, post CAMR,
an individual Native American (who comprise a significant percent of
upper-bound subsistence anglers) will exceed the RfD (an IDI value
greater than 1).
As discussed above, EPA received comments on the consumption rates
of certain ethnic groups that are higher than the subsistence angler
consumption rate that EPA relied on for purposes of this analysis.
Specifically, members of the Ojibwe Great Lakes Tribes commented that
during their fall spearing season they may consume between 156 and 241
grams of fish per day, and during their spring spearing season, they
may consume as much as 293 grams/day. For a number of reasons, EPA
found the data to be of limited value. First, the data have not been
peer reviewed and thus EPA is reluctant to rely on them for regulatory
purposes. Second, commenters did not include information on annual
average consumption rates or the percentage of those fish consumers
that are women of childbearing age. Third, based on EPA's information,
the Tribes do not reside in an area that appears to be significantly
impacted by utility Hg emissions. Thus, despite having extremely high
consumption rates, there are no data in the record that suggest that
members of the Tribe would be exposed above the RfD (an IDI value
greater than 1) as a result of utility emissions. And again, as
discussed in greater detail below, exposure above the RfD does not
necessarily equate to adverse effects.
3. The RfD Is An Appropriate Health Benchmark
As described in section VII.B., in general, the RfD is ``an
estimate (with uncertainty spanning perhaps an order of magnitude) of a
daily exposure to the human population (including sensitive subgroups)
that is likely to be without an appreciable risk of deleterious effects
during a lifetime.'' \53\ EPA's RfD for Methylmercury is 0.1 [mu]g/kg
bw/day, which is 0.1 microgram of Hg per day for each kilogram of a
person's body weight. Since the most sensitive subpopulations are
factored into the RfD, its use is thought to be protective of all life
stages without additional uncertainty factors or adjustments. The
National Academy of Sciences (NAS) reviewed the toxicological effects
of Methylmercury and concluded that ``[o]n the basis of its evaluation,
the committee's consensus is that the value of EPA's current RfD for
Methylmercury, 0.1 [mu]g/kg per day, is a scientifically justifiable
level for the protection of public health.'' \54\
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\53\ See http://www.epa.gov/iris/subst/0073.htm.
\54\ See NAS at page 11 (emphasis added).
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EPA views the level of the RfD as establishing the overall context
for assessing the health effects of ingesting utility-attributable
Methylmercury. As noted above, in regulating HAPs that constitute
threshold pollutants, EPA has stated that the risks associated with
exposures below the RfD generally should be considered to be
acceptable, and that the emissions associated with those exposures need
not be regulated further under section 112.
However, the RfD should not be considered a bright line. At
exposures above the RfD, ``adverse health effects are possible,'' but
such exposures ``[do] not necessarily mean that adverse effects will
occur.'' Indeed, the World Health Organization has concluded that a
level equal to 2.3 times EPA's Methylmercury RfD is protective of human
health.
4. Risks Remaining After Implementation of CAIR, and Even More So After
CAMR, Are Acceptable
Applying the risk factors identified above to utility Hg emissions
in the 112(n)(1)(A) context, EPA concludes that utility Hg emissions
remaining after implementation of CAIR, and even more so after CAMR, do
not pose unacceptable hazards to public health. The overwhelming
majority of the general public and high-end fish consumers (at least
through the 99th percentile of recreational anglers) are not expected
to be exposed above the methylmercury RfD (an IDI value greater than
1). While the possibility exists that a very small group of people may
be exposed above the RfD (an IDI value greater than 1), significant
uncertainties exist with respect to the existence and
[[Page 16025]]
actual size of such a group. There are also significant uncertainties
concerning the extent to which such exposure might exceed the RfD (an
IDI value greater than 1) and whether exposure at such levels would
cause adverse effects. See TSD. EPA intends to continue to investigate
the size and extent to which certain groups might be exposed above the
RfD (an IDI value greater than 1), and reserves the right to revisit
its risk acceptability determination if future information warrants.
In the meantime, however, given the size of the population,
including sensitive subpopulations, that after implementation of CAIR
and, independently, CAMR, will be below the RfD (an IDI value of less
than 1); the uncertainty of the size and the level to which certain
groups may be exposed above the RfD (an IDI value greater than 1); the
uncertainties that adverse effects will be experienced by such groups
even at levels significantly above the methylmercury RfD (an IDI value
greater than 1); and the nature of those potential adverse effects (see
TSD), EPA, in its expert judgment, concludes that utility Hg emissions
do not pose hazards to public health, and therefore that it is not
appropriate to regulate such emissions under section 112.
5. Section 112(f) ``Residual Risk'' Analysis
Some commenters have argued that, in determining whether utility
HAPs pose a hazard to public health, EPA is bound to the mandates of
section 112(f). In other words, some have argued that unless we can
conclude that the imposition of the CAA requirements on utility HAP
emissions ``provide[s] an ample margin of safety to protect public
health,'' we must regulate utilities under section 112. We disagree.
Section 112(n)(1)(A) governs our decision whether to regulate utilities
under section 112, not 112(f). Had Congress intended us to apply the
same standard, it could have used identical words to those found in
section 112(f) or referenced it directly. It did not. Instead, Congress
instructed EPA to assess whether utility HAP emissions cause ``hazards
to public health.''
Nevertheless, as explained above, in assessing whether remaining
utility HAP emissions cause ``hazards to public health,'' EPA used
essentially the same analysis that it would use in assessing the human
health prong of a 112(f) determination.\55\ The factors laid out in the
``benzene'' analysis for assessing acceptable risk to public health
under 112(f) are generally relevant to assessing hazard under
112(n)(1)(A). Thus, even if EPA were required to do a 112(f) analysis
in determining whether utility Hg emissions pose public health hazards,
it is very likely that the conclusion would have been the same, even if
the methodology might have been slightly different.
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\55\ It should be noted that section 112(f) requires
consideration of effects on the environment in addition to human
health. In contrast, 112(n) requires a narrower assessment.
---------------------------------------------------------------------------
As noted above, section 112(f) expressly incorporates EPA's pre-
1990 two-part inquiry for evaluating what level of emission reduction
is needed to provide an ample margin of safety to protect public
health. See CAA section 112(f)(2)(B) (incorporating EPA's two-part
ample margin of safety inquiry, set forth at 54 FR 38044 (Sept. 14,
1989), which implemented the requirements of section 112 of the 1977
CAA). Under this approach, we must first determine what level is
``acceptable'' based exclusively upon the Administrator's determination
of the risk to health at a particular emission level. Vinyl Chloride,
824 F.2d at 1164.\56\ The Court stressed, however, that ``safe'' in
this context does not mean ``risk-free.'' Rather, the Agency must make
a determination about what is safe ``based upon an expert judgment with
regard to the level of emission that will result in an ``acceptable''
risk to health,'' taking into account the many every day activities
that entail health risks but are not considered to be unsafe. Id. at
1165.
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\56\ The Vinyl Chloride court did note, however, that under
certain circumstances it might be appropriate to combine the two
steps into one. Specifically, the court stated that ``[i]f the
Administrator finds that some statistical methodology removes
sufficiently the scientific uncertainty present in this case, then
the Administrator could conceivably find that a certain
statistically determined level of emissions will provide an ample
margin of safety. If the Administrator uses this methodology, he
cannot consider cost and technological feasibility: these factors
are no longer relevant because the Administrator has found another
method to provide an `ample margin' of safety.'' 824 F.2d at 1165,
fn 11.
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In this regard, we also note that section 112(f) makes a
distinction between pollutants classified as ``known, probable or
possible carcinogens'' and other hazardous air pollutants such as Hg.
For possible carcinogens, the Agency must set a residual risk standard
if ``the individual most exposed to emissions from a source'' is
subject to a risk above a certain level. This additional requirement
does not apply to other hazardous air pollutants. Therefore, in
determining whether any level of Hg emission is `acceptable' under
112(f), we would use the same basic approach we have used in this case.
Although we would evaluate the risk to the maximum exposed individual,
which we essentially did for purposes of assessing the hazards posed by
utility emissions under section 112(n)(1)(A), we believe that ``the
distribution of risks in the exposed population, incidence, the science
policy assumption and uncertainties associated with the risk measures,
and the weight of evidence that a pollutant is harmful to health are
[also] important factors to be considered'' in making a decision as to
whether a given level of emissions is acceptable. 54 FR at 38044.
Then, ``[i]n the ample margin decision [the second step], the
Agency again considers all of the health risk and other health
information considered in the first step. Beyond that information,
additional factors relating to the appropriate level of control will
also be considered, including costs and economic impacts of controls,
technological feasibility, uncertainties, and any other relevant
factors.'' 54 FR 38046.
As explained in section H.3. above, applying the general principles
articulated in the Vinyl Chloride decision and the benzene rule, the
Agency has concluded that power plant Hg emissions remaining after
CAIR, and even more so after CAMR, do not pose hazards to public
health. This determination was based on health considerations alone, as
would be the case under the first step of a 112(f) analysis. Under the
second step of a 112(f) analysis, we would then consider both the
benefits and costs of further emission reductions. Based on what we
know about the uncertainties and nature of the potential adverse
effects associated with Hg exposure, the extent to which the public,
including sensitive subpopulations, is exposed to Hg, and the extent to
which such exposure could be reduced by further reducing Hg emissions
from U.S. power plants, we have concluded that the cost of requiring
further reductions in Hg emissions from power plants would
significantly outweigh any benefits. Therefore, if we were proceeding
under section 112(f), we would likely conclude that CAIR, and even more
so CAMR, not only protects public health, but does so with an ``ample
margin of safety.''
I. The Final CAMR Will Not Lead to Localized ``Utility Hot Spots''
1. What Is a ``Utility Hot Spot''?
As we said in the preamble to the proposed rule, Hg emissions from
power plants sometimes are deposited locally near the plant (i.e.,
within 25 km),
[[Page 16026]]
specifically emissions of oxidized and particulate Hg. Nearby
waterbodies may be a source of fish consumption for recreational and/or
subsistence fishers, and thus local Hg deposition in nearby waterbodies
could be a source of what some refer to as ``hot spots.'' In the
proposed rule, we suggested that a ``power plant may lead to a hot spot
if the contribution of the plant's emissions of Hg to local deposition
is sufficient to cause blood Hg levels of highly exposed individuals
near the plant to exceed the RfD.'' (See 69 FR 4702.)
Based on additional analysis and consideration of the ``hot spot''
issue and to ensure that stakeholders have a common understanding of
how EPA uses the term, we define a ``utility hot spot'' as ``a
waterbody that is a source of consumable fish with Methylmercury tissue
concentrations, attributable solely to utilities, greater than the
EPA's Methylmercury water quality criterion of 0.3 mg/kg.'' We believe
that the water quality criterion is an appropriate indicator of a ``hot
spot,'' given that the Methylmercury exposure pathway of greatest
concern is fish consumption and that the water quality criterion was
back calculated from the Methylmercury RfD using a high-end fish
consumption rate.
2. EPA Does Not Believe That There Will Be Any Hot Spots After
Implementation of CAIR and CAMR
As explained elsewhere in this preamble and in the TSD, for
purposes of today's notice, EPA modeled utility Hg deposition, before
and after implementation of CAIR and CAMR, using the Community Multi-
Scale Air Quality (``CMAQ'') model, a three-dimensional eulerian grid
model. CMAQ is the most sophisticated Hg dispersion model in existence.
It uses a ``one-atmosphere'' approach and addresses the complex
physical and chemical interactions known to occur among multiple
pollutants in the free atmosphere.\57\ The spatial resolution (i.e.,
the ability to observe concentration or depositional gradients/
differences) of the gridded output information from CMAQ for purposes
of this analysis is 36 km.
---------------------------------------------------------------------------
\57\ In simulating the transport, transformation, and deposition
of pollutants, CMAQ resolves 14 vertical layers in the atmosphere,
and employs finer-scale resolution near the surface of the boundary
layer to simulate deposition to both terrestrial and aquatic
ecosystems. CMAQ atmospheric transport is defined using a higher-
order meteorological model, commonly the Fifth-Generation
Pennsylvania State University/National Center for Atmospheric
Research mesoscale model (MMM5).
---------------------------------------------------------------------------
We believe that this an appropriate scale given the exposure
pathway. First, because much of the Hg deposited on the watershed of
different ecosystems will eventually enter waterbodies through
subsurface inflow and runoff, we consider a watershed scale analysis to
be more appropriate than finer scale resolution that may only describe
direct inputs to surface waters. Second, in larger waterbodies (i.e.,
the Great Lakes) where there is substantial fishing activity, the
higher trophic level fish species consumed by humans are likely
migratory and the accumulation of Hg by these species will represent an
aggregated signal from deposition over a wider area (e.g., the entire
waterbody within a watershed.) Since we are concerned about the
cumulative dose over weeks and months from repetitive consumption of
fish containing methylmercury, this fishing behavior should be
considered in the exposure pathway. Based on the above considerations,
we conclude that the HUC-8 watershed is the appropriate unit of measure
for analysis. While this analysis covers the vast majority of the U.S.
population that may be exposed to emissions from U.S. power plants, we
acknowledge that there are inherent uncertainties at the extreme tails
of the exposure distribution. We continue to advance the state of the
science and the associated models to better understand the tail of this
exposure distribution.
As discussed in section VII.D. of today's notice, EPA used fish
tissue data from the National Listing of Fish and Wildlife Advisories
and the National Fish Tissue Survey to determine Methylmercury fish
tissue concentrations for numerous sample sites throughout the country.
We then used CMAQ to determine the amount of utility Hg deposition, in
conjunction with Mercury Maps (which associates an increment of change
in Hg deposition with an equal change in Methylmercury fish tissue
concentrations) to predict what fish concentrations at those sample
sites would be after implementation of CAIR and CAMR. As discussed in
section VII.E., those analyses conclude that none of the sample sites
will exceed, as a result of utility emissions, the water quality
criterion of 0.3 mg/kg. In fact, our analysis shows that fish tissue
Methylmercury concentrations attributable to utility Hg emissions will
be significantly below the water quality criterion. By 2020, after
CAIR, levels at the 50th, 90th, 99th percentiles and maximum value
sample site are predicted to be 0.01, 0.03, 0.10, and 0.25 mg/kg,
respectively. After CAMR, levels at the 50th, 90th, 99th percentiles
and maximum value sample site are predicted to be 0.01, 0.03, 0.09, and
0.19 mg/kg, respectively. Therefore, based on the information available
to us at this time, our analyses indicate utility Hg emissions, after
implementation of either CAIR or CAMR, will not result in ``hot
spots.''
EPA conducted a similar analysis in its 1998 Utility Report to
Congress (``Utility Study'') using the Industrial Source Complex
Version 3 (``ISC3'') model. (See TSD) EPA analyzed four model plants
representing four utility boilers: Large coal-fired, medium coal-fired,
small coal-fired, and medium oil-fired. Each of these plants was also
modeled at two generic sites: A humid site east of the 90 degrees west
longitude, and a more arid site west of the 90 degree west longitude.
(See Utility Study at 7-29). Hg deposition was modeled at a
hypothetical lake located at three distances for each model site: 2.5,
10, and 25 km. The results of that analysis showed that under only one
modeled scenario was the Methylmercury water quality criterion
exceeded. Specifically, the model predicted that a hypothetical lake
located 2.5 km from a large eastern coal-fired utility would experience
Methylmercury fish tissue concentration of 0.43 mg/kg. None of the
other 23 model facilities/lake combinations exceeded the water
criterion. (See Utility Study at 7-37).
For a number of reasons more fully explained in our TSD, even
though only one facility/lake combination exceeded the water quality
criterion, we believe that the analysis done for the 1998 Utility Study
was conservative and, hence, over predicted near-field Hg deposition
and corresponding fish tissue concentrations in almost all situations.
That analysis was a screening analysis and thus was conservative by
design. For example, it did not incorporate a sophisticated treatment
of the atmospheric chemistry and phase-transition behavior of Hg, as we
have included in our CMAQ analysis, and our understanding of wet and
dry deposition processes for Hg has improved significantly since then.
As a result, we judge that the CMAQ model results represent a more
accurate representation of near-field Hg impacts than can be obtained
using the ISC3 modeling approach. See the discussion above about why
the CMAQ model appropriately represents near-field deposition.
There are other factors that lead EPA to conclude that the Utility
Study analysis overstated fish-tissue methylmercury concentrations in
most situations. Based on the BAFs considered, the hypothetical
ecosystem described in the RTC is more sensitive
[[Page 16027]]
than three out of four ecosystems chosen for the case studies (see
Table 4-6, page 25 of Ecosystem Scale Modeling for Mercury Benefits
Analysis) and is less sensitive than one (Lake Barco). Comparing these
case studies to empirically derived BAFs characterized by the Office of
Water indicates that modeled fish tissue responses in three of four
case studies had empirically derived BAFs that fell between the 5th and
50th percentiles of the geometric mean of field-measured BAFs for
trophic level 4 species obtained from the published literature (EPA
2000). The model ecosystem described in the RTC fell between the 50th
and 95th percentile for BAFs, and one of the case studies (Lake Barco)
exceeded the 95th percentile.
Some limitations to the BAF approach deserve mention. Because
Methylmercury concentrations in the water column are highly variable,
empirically-derived BAFs are inherently underdetermined and have
limited predictive power. A more credible approach based on our current
knowledge is to forecast changes in fish Hg concentrations using
information on the food-web dynamics (``bioenergetics'') of different
ecosystems. Such a model (BASS) was applied in one of the case studies
described in Chapter 3 of the RIA for CAMR, and showed that while the
BAFs calculated from the outputs of the bioenergetics-based
bioaccumulation model were within a factor of 2 of the empirically
derived BAF used in the SERAFM model, the empirically derived fish Hg
concentrations were more conservative than the BASS model for this one
ecosystem. (See TSD). Thus, the above information suggests that our RTC
analysis may have over predicted fish-tissue methylmercury
concentrations in many ecosystems that could be impacted by Hg
deposition from U.S. power plants. However, it is important to note
that fish tissue methylmercury concentrations due to power plants may
be higher in some ecosystems (for example, ecosystems similar to Lake
Barco described in Ch. 3 of the CAMR RIA).
For all the above described reasons, we think our current modeling
approach as described in the TSD provides for a more advanced, state-
of-the-science assessment of the atmospheric fate, transport,
deposition, and cycling of Hg through the environment than the modeling
approach used in the Utility Study. For these reasons, we have no
evidence that utility Hg emissions after CAIR (and even more so after
CAMR) will result in hot spots.
Based on our experience with the Title IV acid rain program and our
modeling using IPM, we believe that the cap-and-trade approaches
adopted under CAIR and CAMR will reduce Hg exposure in most areas and
create strong economic incentives for the reduction of Hg emissions in
the future.
First, modeling runs suggest that large coal-fired utilities
contribute more to local Hg deposition than medium-sized and smaller
coal-fired utilities.\58\ However, under a cap-and-trade system, large
utilities are more likely to over-control their emissions and sell
resulting emission allowances than smaller utilities, which are less
likely to be the source of a local hot spot. Under basic utility
economics of capital investment, when capital is limited, up-front
capital costs of control equipment are significant, and where emission-
removal effectiveness (measured in percentage of removal) is unrelated
to plant size, it makes more economic sense for a company to allocate
pollution-prevention capital to its larger facilities where more
allowances can be earned, than to its smaller ones. In other words, we
would expect economies of scale of pollution control investment to be
made at larger plants. Moreover, newer plants tend to be larger. Since
newer plants have longer expected lifetimes, providing a longer return
on investment, we would expect this to be an incentive for these larger
facilities to choose to control and sell credits.
---------------------------------------------------------------------------
\58\ Indeed, the one model utility in the Utility Study analysis
that exceeded the water quality criterion at a hypothetical lake
within 2.5 km was an eastern large coal-fired utility. Given the
tendencies for larger facilities to control under a cap-and-trade
system, we do not anticipate that larger plants will cause localized
hot spots.
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Indeed, as part of its analysis of the President's 2003 Clear Skies
initiative, EPA analyzed Hg emissions reductions under a cap-and-trade
mechanism. In the Clear Skies example, the greatest emissions
reductions were projected to occur at the electric generating sources
with the highest Hg emissions. This pattern is similar to that observed
in the SO2 emissions trading program under the Acid Rain
Program. Under Clear Skies, compared to a base case of existing
programs, Hg 2+ emissions (which tend to be
deposited locally, i.e., within 25 kilometers) from power plants
located up to 10 kilometers from a water body were projected to
decrease by over 60 percent by 2020.
Second, the types of Hg that are deposited locally--Hg
2+ and Hgp--are controlled by the same
equipment that controls PM, SO2, and NOX. Thus,
as utilities invest in equipment to comply with EPA's new PM and ozone
standards (e.g., the CAIR rule that was signed on March 10, 2005 and
new State Implementation Plans (SIPs) for PM and ozone), the Agency
expects ``co-benefit'' Hg reductions.
Moreover, EPA's IPM modeling for today's action predicts that
larger emitters generally are expected to reduce the most, as was our
experience with the Acid Rain Program. Through our CMAQ modeling, we
further predict utility-attributable deposition reductions in areas
where hotspots would otherwise potentially occur. As described in
section VII.E., the median deposition level is reduced by only 8
percent when utilities emissions are zeroed out in 2001, but in areas
with the highest deposition levels, zeroing out utilities reduces the
99th percentile deposition level by 15 percent. After implementation of
CAIR in 2020, areas with high levels of utility deposition receive a
larger reduction in utility-attributable Hg deposition relative to
areas with a relatively small level of utility-attributable deposition.
For all these reasons, we do not anticipate that our final CAMR
rule will result in local Hg hot spots; to the contrary, we anticipate
that our cap-and-trade CAMR will actually eliminate hot spots that may
have previously existed.
In addition to reductions required by the CAIR and CAMR caps,
states have the authority to address local health-based concerns
separate from these programs. Although more stringent state regulations
would reduce the flexibility of a cap-and-trade system, states
nevertheless have such authority.
3. Continued Evaluation of Utility Hg Emissions
For all the reasons discussed above and elsewhere in this preamble,
EPA does not believe that CAIR or CAMR will result in utility-
attributable hot spots. That said, we recognize that even our state-of-
the-art models and inputs have certain limitations that make it
impossible for us to definitively conclude that there are no
circumstances under which a hot spot could result even after full
implementation of CAIR and CAMR. However, in order for a hot spot to
occur, there would have to be an alignment of key environmental
factors, such as meteorology, deposition, and ecosystem processes in
conjunction with a large uncontrolled near-field utility unit or a
collection of such units. The likelihood of these factors converging is
remote. Nevertheless, we intend to monitor this situation closely and
continue to advance the state of the science of Hg transport and fate.
In that
[[Page 16028]]
regard, if we receive new information that raises the possibility of
utility-attributable hotspots, we will evaluate the situation and take
appropriate action.
We believe that we have the authority under the Act to address
future hotspots appropriately. Indeed, today we have identified other
authorities under the CAA through which we can obtain Hg reductions
from coal-fired Utility Units--either by regulating Hg directly, or
indirectly as the result of co-benefits. The 1998 Utility Study also
identifies other requirements of the Act with which Utility Units must
comply that can result in HAP reductions, including Hg. Because we do
not currently have any facts before us that would lead us to conclude
that utility-attributable hotspots exist, we do not at this time reach
any conclusion as to which statutory authority we would use to address
such a fact-specific situation because it necessarily depends on the
facts.
For example, if in the future we determine that utility-
attributable hotspots exist and that those hotspots occur as the result
of Hg emissions from coal-fired Utility Units, we may promulgate a
tighter section 111 standard of performance, provided we determine the
technology can achieve the contemplated reductions. We could revise the
standard of performance by adjusting the cap-and-trade program to limit
trading by high-emitting Utility Units. As the DC Circuit has
recognized, we have discretion to weigh the statutory factors
identified in section 111(a), which include cost, in setting a standard
of performance. Lignite Energy Council v. EPA, 198 F.3d 930 (DC Cir.
1999). We therefore believe that under section 111, we can evaluate the
cost of emission reduction in the context of the identified hotspots,
and we may reasonably conclude that the additional cost of a more
stringent standard is appropriate in light of the health concern
associated with the hotspots. Alternatively, we may in the future
identify utility-attributable hotspots and determine that such hotspots
can be addressed by virtue of Hg co-benefits control achieved through
the promulgation of other requirements. Thus, although we cannot
conclude today which statutory authority we would implement to address
utility-attributable hotspots because that determination necessarily
hinges on the facts associated with the identified hotspots, we do
conclude that were such a situation to occur, we believe that EPA has
adequate authority to address any such situation that may arise in the
future.
J. The Global Pool of Hg Emissions
1. Background
As explained above, Hg is emitted into the environment in different
ways. About one-third of the Hg in the atmosphere is from human-caused
activities (``anthropogenic''), one-third is from natural processes
(such as volcanic eruption, groundwater seepage and evaporation from
the oceans), and one-third constitutes re-emitted emissions, which is
Hg from human-caused activities or natural processes that is emitted
into the atmosphere, deposited and then re-emitted into the atmosphere.
United States anthropogenic Hg emissions are estimated to account for
about three percent of the global pool of Hg emissions, and United
States (``domestic'') utilities are estimated to account for about one
percent of that total global pool. See Utility Study at 7-1 to 7-2, 69
FR at 4657-58 (January 20, 2004). The global pool therefore includes
all human-caused activities that occur both within the United States
and abroad, all emissions that result from natural processes anywhere
in the world, and re-emitted Hg.
To place the Hg emissions from domestic Utility Units in context,
EPA modeled different scenarios that analyze the effect of domestic
utility Hg emissions in the context of the global pool. We describe
that modeling in detail above.
Our modeling shows that in virtually all instances, the utility-
attributable methylmercury levels are a very small fraction of the
overall methylmercury levels. For 16 percent of the modeled sites,
overall levels of methylmercury in fish tissue in 2020 are projected to
be above the 0.3 mg/kg water quality criterion. At the 90th percentile,
in 2020, after implementation of CAIR, overall levels are projected at
0.79 mg/kg, and at the 99th percentile, at 1.64. The greatest fraction
of these methylmercury levels are attributable to non-air sources,
including mines and chloralkali plants, and uncontrollable air sources,
including international emissions from industrial and utility sources.
In virtually all of these instances, the Utility-attributable
methylmercury levels are a very small fraction of the overall
methylmercury levels. For the highest 10 percent of utility-
attributable methylmercury fish tissue levels, utility-attributable
methylmercury accounted for a maximum of 9 percent of total
methylmercury concentrations, and an average of only 4 percent.
Clearly, even at locations with high levels of utility Hg deposition,
other sources of Hg contribute most of the methylmercury.
2. Even Examining Utility Hg Emissions in the Context of the Global
Pool, We Cannot Conclude That It Is Appropriate to Regulate Coal-Fired
Utility Units Under CAA Section 112
Our conclusions in sections VI.J and VI.K above are based solely on
our analysis of Hg emissions from coal-fired Utility Units. See
generally 65 FR 79,826-29 (explaining that Hg from coal-fired units is
the HAP of greatest concern); Utility Study, ES-27 (same). We focused
our analysis in this regard because EPA has interpreted section
112(n)(1)(A) to examine the hazards to public health that are ``a
result of'' Utility Units. See CAA section 112(n)(1)(A). As explained
in section III above, the focus in section 112(n)(1)(A) on emissions
``result[ing]'' from Utility Units is significant, particularly when
contrasted against other provisions of the Act, such as section
110(a)(2)(D). In section 110(a)(2)(D), Congress sought to regulate any
air pollutant that will ``contribute to'' nonattainment. Thus, under
section 110(a)(2)(D), we can regulate a pollutant if it ``contributes''
to a nonattainment problem, but does not itself cause the problem. EPA
has concluded that section 112(n)(1)(A) is different, where Congress
directed EPA to study the hazards to public health ``reasonably
anticipated to occur as a result of emissions of'' Utility Units.
(emphasis added)
Moreover, Congress' focus on the hazards to public health resulting
from Utility Units may reflect Congress' recognition of the unique
situation posed by Hg, which is that Hg emissions from domestic
utilities represent less than one percent of the global pool. Indeed,
Congress specifically addressed Hg in other provisions of section
112(n). For example, under section 112(n)(1)(B), Congress required EPA
to complete a study addressing Hg emissions from Utility Units and
other sources of Hg. See CAA section 112(n)(1)(B); see also CAA Section
112(n)(1)(C) (requiring National Institute of Environmental Health
Sciences to determine the threshold level of Hg exposure below which
adverse human health effects are not expected to occur).
Nevertheless, even were we to examine hazards to public health on a
broader scale by focusing on the global Hg pool, our conclusion
(discussed above in Section IV.A.) that it is not appropriate to
regulate coal-fired Utility Units under section 112 on the basis of Hg
emissions would be the same. Our analyses in support of that conclusion
would differ, however, because we
[[Page 16029]]
would be assessing whether it is appropriate to regulate Utility Units
under section 112 by reference to a different level of Hg emissions. As
explained in section III of this notice, we have discretion, in
determining whether regulation under section 112 is appropriate, to
consider other factors and, in particular, any unique facts and
circumstances associated with the HAP emissions at issue. Here, the
unique circumstance is that domestic Utility Units represent only one
percent of the global pool. Our modeling shows that were we to prohibit
all Hg emissions from domestic utilities in this country, such
regulation would result in only a very small improvement in
methylmercury levels in the waterbodies that exceed the methylmercury
water quality criteria. Therefore, precluding all Hg emissions from
coal-fired powerplants would, in effect, force such plants out of
business, yet reduce virtually none of the risks to public health
stemming from the global Hg pool.
In these circumstances, we find that it is not appropriate to
regulate coal-fired Utility Units under section 112 on the basis of the
global Hg pool because the health benefits associated with such
regulation would be nominal and the costs extreme. It is also not
appropriate to regulate Hg emissions from coal-fired utility units
remaining after imposition of the requirements of the Act because the
global sources contributing most significantly to the remaining public
health hazards are not domestic utilities and the sole question before
us under section 112(n)(1)(A) is whether it is appropriate to regulate
Utility Units under section 112 of the Act.\59\
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\59\ See 36 Cong. Rec. S16895, S16899 (daily ed. Oct. 27, 1990)
(Statement of Senator Burdick, member of the Conference Committee
and Chairman of the Committee on Environment and Public Works)
(``Under section 112(n) utility emissions are exempt from air toxics
regulation until studies are completed and the Administrator
determines, based on the studies, that air toxics regulation is
warranted. The hazardous substance of greatest concern here is Hg.
The Senate bill required Hg reductions from coal-fired units. The
Senate provision could not be sustained by the scientific facts.
What little is known of Hg movement in the biosphere, suggests that
its long residence time makes it a long-range transport problem of
international or worldwide dimensions. Thus, a full control program
in the United States requiring dry scrubbers and baghouses to
control Hg emissions from coal-fired power plants would double the
costs of acid rain control with no expectation of perceptible
improvement in public health in the United States. I am pleased the
conferees adopted the House provision on hazardous air pollutants
with respect to Utility Units.'')
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K. Further Study
The behavior of Hg in the atmosphere and in aquatic systems, and
the human health effects of Hg are areas of much interest and activity
within the scientific and health research communities. In addition, our
ability to quantify and value the effects that changes in Hg releases
may have to human health is continuing to evolve. Furthermore,
technologies and techniques for limiting Hg emissions from power plants
are also rapidly advancing. EPA will continue to monitor developments
in all these areas, as well as continuing its own efforts to advance
the state of the science. One of the benefits of today's approach is
that it provides a flexible structure that could be modified to
accommodate new information should it become available.
VII. EPA'S Authority to Regulate HAP From Utility Units Under CAA
Section 111
As explained in sections IV and VI above, we conclude today, among
other things, that EPA's December 2000 appropriate and necessary
finding lacked foundation because it failed to consider the HAP
reductions that could be obtained through implementation of section
111, and therefore whether it was ``necessary'' to regulate under
section 112. We decide today that it is not ``necessary'' to regulate
utility HAPs under section 112, in particular because of our
authorities to effectively reduce utility HAPs under CAA sections
110(a)(2)(D) and 111.\60\
We describe below the regulatory scheme under section 111 and EPA's
authority to regulate HAP emissions under that section. We also
describe the recently issued Clean Air Mercury Rule (``CAMR''), which
implements CAA section 111. Finally, we demonstrate that the CAMR rule,
once implemented, will result in levels of Hg emissions from coal-fired
Utility Units that pose no hazards to public health.
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\60\ We also conclude today, as discussed in detail above, that
Hg emissions from coal-fired Utility Units remaining after
implementation of section 110(a)(2)(D) do not result in hazards to
public health. See Sections V and VI. Section 111, which is the
focus of this section of the preamble, constitutes an independent
basis for our actions today, because that provision, once
implemented, will effectively address any Hg emissions from coal-
fired Utility Units, and for that reason, Hg emissions from coal-
fired Utility Units that remain ``after imposition of the
requirements of th[e] Act do not result in hazards to public
health.'' CAA Section 112(n)(1)(A).
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A. Overview of the Requirements of Section 111
CAA section 111 creates a program for the establishment of
``standards of performance.'' A ``standard of performance'' is ``a
standard for emissions of air pollutants which reflects the degree of
emission limitation achievable through the application of the best
system of emission reduction, which (taking into account the cost of
achieving such reduction, any nonair quality health and environmental
impacts and energy requirements), the Administrator determines has been
adequately demonstrated.'' CAA section 111(a)(1).
For new sources, EPA must first establish a list of stationary
source categories, which, the Administrator has determined ``causes, or
contributes significantly to, air pollution which may reasonably be
anticipated to endanger public health or welfare.'' CAA section
111(b)(1)(A)). EPA must then set federal standards of performance for
new sources within each listed source category. (CAA section
111(b)(1)(B)). Like section 112(d) standards, the standards for new
sources under section 111(b) apply nationally and are effective upon
promulgation. (CAA section 111(b)(1)(B)).
Existing sources are addressed under section 111(d) of the CAA. EPA
can issue standards of performance for existing sources in a source
category only if it has established standards of performance for new
sources in that same category under section 111(b), and only for
certain pollutants. (CAA section 111(d)(1)). Section 111(d) authorizes
EPA to promulgate standards of performance that states must adopt
through a SIP-like process, which requires state rulemaking action
followed by review and approval of state plans by EPA. If a state fails
to submit a satisfactory plan, EPA has the authority to prescribe a
plan for the state. (CAA section 111(d)(2)(A)).
B. EPA's Authority to Regulate HAP Under Section 111
Section 111(b) covers any category of sources that causes or
contributes to air pollution that may reasonably be anticipated to
endanger public health or welfare and provides EPA authority to
regulate new sources of such air pollution. EPA included Utility Units
on the section 111(b) list of stationary sources in 1979 and has issued
final standards of performance for new Utility Units for pollutants,
such as NOX, PM, and SO2. See 44 FR 33580; June
11, 1979; Subpart Da of 40 CFR Part 60. Nothing in the language of
section 111(b) precludes EPA from issuing additional standards of
performance for other pollutants, including HAP, emitted from new
Utility Units. Moreover, nothing in section 112(n)(1)(A) suggests that
Congress sought to preclude EPA from regulating Utility Units under
section 111(b). Indeed, section 112(n)(1)(A)
[[Page 16030]]
provides to the contrary, in that it calls for an analysis of utility
HAP emissions ``after imposition of the requirements of th[e] Act,''
which we have reasonably interpreted to mean those authorities that EPA
reasonably anticipated at the time of the Study would have reduced
utility HAP emissions.
EPA received numerous comments concerning its authority under
section 111 to regulate HAP from Utility Units. Those comments focused
largely on EPA's authority to regulate existing units under section
111(d). As explained below, EPA has reasonably interpreted section
111(d) as providing authority to regulate HAP from existing Utility
Units.
Unlike section 111(b), section 111(d) specifically references CAA
section 112. The import of that reference is not clear on the face of
Public Law 101-549, which is the 1990 amendments to the CAA, because
the House and Senate each enacted a different amendment to section
111(d). The Conference Committee never resolved the differences between
the two amendments and both were enacted into law as part of section
111(d). EPA is therefore confronted with the highly unusual situation
of an enacted bill signed by the President that contains two different
and inconsistent amendments to the same statutory provision.
1. Overview of the Two Amendments in Section 111(d)
An important starting point for evaluating the two amendments to
section 111(d) in 1990 is the 1977 Act. Section 111(d) of the 1977 CAA
provides, in pertinent part:
The Administrator shall prescribe regulations which shall
establish a procedure similar to that provided by section 7410 of
this title under which each State shall submit to the Administrator
a plan which (A) establishes standards of performance for any
existing source for any air pollutant (i) for which air quality
criteria have not been issued or which is not included on a list
published under section 7408(a) or 7412(b)(1)(A) of this title, but
(ii) to which a standard of performance under this section would
apply if such existing source were a new source. * * *
42 U.S.C.A. 7411(d) (West 1977); Public Law 95-95. The above language
provides that standards of performance under section 111(d) cannot be
established for any pollutant that is listed as a ``hazardous air
pollutant'' under section 112(b)(1)(A) of the 1977 CAA.
In 1990, Congress significantly amended the CAA. Among other
things, it significantly amended section 112, it enacted Title IV of
the CAA, which includes numerous provisions that are directly
applicable to Utility Units, and it amended section 111(d). Both the
House and the Senate bills included different amendments to section
111(d), and both of those amendments were enacted into law.
The first amendment, which is the House amendment, is contained in
section 108(g) of Public Law 101-549. That section amends section
111(d)(1)(A)(i) of the 1977 CAA by striking the words ``or
112(b)(1)(A)'' from the 1977 CAA and inserting in its place the
following phrase: ``or emitted from a source category which is
regulated under section 112.'' The second amendment to section 111(d),
which is the Senate amendment, is labeled a ``conforming amendment''
and is set forth in section 302 of Public Law 101-549. That section
amends CAA section 111(d)(1) of the 1977 CAA by striking the reference
to ``112(b)(1)(A)'' and inserting in its place ``112(b).'' The two
amendments are reflected in parentheses in the Statutes at Large as
follows:
The Administrator shall prescribe regulations which shall
establish a procedure similar to that provided by section 7410 of
this title under which each State shall submit to the Administrator
a plan which (A) establishes standards of performance for any
existing source for any air pollutant (i) for which air quality
criteria have not been issued or which is not included on a list
published under section 7408(a) (or emitted from a source category
which is regulated under section 112) [House amendment,] (or 112(b))
[Senate Amendment,] but (ii) to which a standard of performance
under this section would apply if such existing source were a new
source. * * *
The United States Code does not contain the parenthetical reference
to the Senate amendment, as set forth in section 302 of Public Law 101-
549. The codifier's notes to this section of the Official Committee
Print of the executed law state that the Senate amendment ``could not
be executed'' because of the other amendment to section 111(d)
contained in the same Act. The United States Code does not control
here, however. The Statutes at Large constitute the legal evidence of
the laws, where, as here, Title 42 of the United States Code, which
contains the CAA, has not been enacted into positive law. See 1 U.S.C.
204(a); United States v. Welden, 377 U.S. 95, 98 n.4 (1964);
Washington-Dulles Transportation Ltd. v. Metropolitan Washington
Airports Auth., 263 F.3d 371, 378 (4th Cir. 2001). We did not receive
any comments disputing either that the Statutes of Large constitute the
legal evidence of the laws in this case, or that the 1990 Act contains
two different amendments to the same statutory provision.\61\
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\61\ Although the notes accompanying the Official Committee
Print do not interpret with the force of law, their conclusion about
the appropriate effect to give these conflicting amendments is
evidence that EPA's conclusion is reasonable.
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2. Overview of Legislative History
As we indicated in the proposal, there is scant legislative history
concerning the two amendments to section 111(d). The most persuasive
legislative history that is relevant to our task of interpreting and
reconciling the House and Senate amendments to section 111(d) is the
final Senate and House bills. Those bills reflect significantly
different treatment of Utility Units under section 112, as well as
different amendments to section 111(d).
We begin our analysis with Senate bill 1630, as passed by the
Senate on April 3, 1990. That bill included a provision concerning
Utility Units. See generally Section 301 (hazardous air pollutants), A
Legislative History of the Clean Air Act Amendments of 1990
(``Legislative History''), Vol III, at 4431-33 (Nov. 1993). Under that
provision, EPA was to conduct a study on the health and environmental
effects of utility HAP emissions within three years of enactment of the
statute. The Senate Bill also required EPA to promulgate section 112(d)
emissions standards for Utility Units within five years of enactment of
the statute. The Senate bill further required EPA to place the study on
utility HAP emissions in the docket for the section 112(d) rulemaking
for Utility Units. Finally, the Senate bill, in a section labeled
``conforming amendments,'' amended section 111(d) by striking the
reference to ``112(b)(1)(A)'' in the 1977 Act and replacing it with
``112(b).'' See generally Section 305 (conforming amendments),
Legislative History, Vol III, at 4534.
The final bill that passed the House in May 1990 stands in stark
contrast to the Senate Bill. The House Bill included section 112(l),
entitled ``Electric Utilities.'' See generally Section 301 (hazardous
air pollutants), Legislative History, Vol II, at 2148-49. That
provision is identical to section 112(n)(1)(A). See 104 Stat. 2558. The
House bill also amended section 111(d) by replacing the words `` or
112(b)(1)(A)'' with ``or emitted from a source category which is
regulated under section 112.'' See Legislative History, Vol. II, at
179.
Finally, the House provision concerning Utility Units is the
provision that was enacted into law as section 112(n)(1)(A). The Senate
approach to
[[Page 16031]]
regulating Utility Units under section 112 did not prevail. See
Legislative History, Vol. I at 1451.
3. EPA's Interpretation of the Two Amendments to Section 111(d)
Neither we, nor commenters, have identified a canon of statutory
construction that addresses the specific situation with which we are
now faced, which is how to interpret two different amendments to the
exact same statutory provision in a final bill that has been signed by
the President. The canon of statutory construction that calls for
harmonizing conflicting statutory provisions, where possible, and
adopting a reading that gives some effect to both provisions is not
controlling here because that canon applies where two provisions of a
statute are in conflict, not where two amendments to the same statutory
provision are in conflict. Nevertheless, we have attempted to follow
the general principles underlying this canon of construction. We also
rely on the legislative history noted above as support for our
interpretation of the two amendments to section 111(d).
Turning first to the House amendment, we noted at proposal that a
literal reading of that amendment is that a standard of performance
under section 111(d) cannot be established for any air pollutant--HAP
and non-HAP--emitted from a source category regulated under section
112. See 69 FR 4685. Certain commenters disagreed with our reading.
They argue instead that a literal reading of the House amendment is
that EPA cannot regulate under section 111(d) any HAP that is emitted
from any source category regulated under section 112. This reading
modifies the plain language of section 111(d), as amended by the House
in 1990, in significant respects. First, it changes the terms ``any
pollutant'' to ``HAP,'' and second, it changes the phrase ``a source
category,'' to ``any source category'' and therefore commenters''
reading of the amendment cannot be characterized as a ``literal'
reading.
Section 111(d), as amended by the House, specifically provides:
Each State shall submit to the Administrator a plan which (A)
establishes standards of performance for any existing source for any
air pollutant * * * which is not emitted from a source category
which is regulated under section 112.
We interpret this language to mean that EPA cannot establish a
standard of performance under CAA section 111(d) for any ``air
pollutant''--including both HAP and non-HAP--that is emitted from a
particular source category regulated under section 112. Thus, under our
interpretation, if source category X is ``a source category'' regulated
under section 112, EPA could not regulate HAP or non-HAP from that
source category under section 111(d). This interpretation reflects the
distinction drawn in section 111(d), as amended by the House, between
``any pollutant'' and ``a source category.'' The phrase ``any
pollutant'' existed prior to the 1990 amendments and therefore it can
be reasonably assumed that when the House amended section 111(d) in
1990, it intentionally chose the words ``a source category,'' as
opposed to ``any source category. Although we recognize that the phrase
``a source category'' is susceptible to different interpretations, in
that it could conceivably mean one or many source categories, we
believe that our interpretation is a permissible construction given the
juxtaposition of the phrases ``any pollutant'' and ``a source
category'' in section 111(d), as amended by the House.
Moreover, consistent with our interpretation of the House
amendment, we believe that the House sought to change the focus of
section 111(d) by seeking to preclude regulation of those pollutants
that are emitted from a particular source category that is actually
regulated under section 112. The legislative history described above is
instructive in this regard. At the same time the House substantively
amended section 111(d), it passed a bill containing a provision
(section 112(l)) that is identical to section 112(n)(1)(A) of the
current act. Section 112(l) of the House bill calls for EPA to examine
how the ``imposition of the requirements of th[e] Act'' would affect
utility HAP emissions. This provision suggests that the House did not
want to subject Utility Units to duplicative or overlapping regulation.
In this regard, the House's amendment to section 111(d) could
reasonably reflect its effort to expand EPA's authority under section
111(d) for regulating pollutants emitted from particular source
categories that are not being regulated under section 112. Such a
reading of the House language would authorize EPA to regulate under
section 111(d) existing area sources which EPA determined did not meet
the statutory criterion set forth in section 112(c)(3), as well as
existing Utility Units (in the event EPA did not decide to regulate
such units under section 112).
The Senate amendment provides that a section 111(d) standard of
performance cannot be established for any HAP that is listed in section
112(b)(1), regardless of whether the source categories that emit such
HAP are actually regulated under section 112. The Senate amendment
reflects the Senate's intent to retain the pre-1990 approach of
precluding regulation under CAA section 111(d) of any HAP listed under
section 112(b). The Senate's intent in this regard is confirmed by the
fact that its amendment is labeled a ``conforming amendment,'' which is
generally a non-substantive amendment. By contrast, the House amendment
is not a conforming amendment.\62\
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\62\ There is a section of the final House bill that includes
conforming amendments. The House amendment to section 111(d) does
not appear in that sectiono of the bill, however. See Legislative
History, Vol. II, at 179, 1986.
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Moreover, the Senate's conforming amendment is consistent with the
Senate's treatment of Utility Units in the final Senate Bill. Unlike
the House bill, the Senate bill did not call for an examination of the
other requirements of the CAA. Nor did it provide EPA discretion to
determine whether Utility Units should be regulated under section 112.
Instead, the Senate bill included a provision that would have required
EPA to establish section 112(d) emission standards for Utility Units by
a date certain. This provision, which was never enacted into law, is
consistent with the Senate's conforming amendment which provides that
HAP listed under section 112(b) cannot be regulated under section
111(d).
Based on the legislative history described above, we believe that
the House amendment, as we have interpreted it, is wholly consistent
with section 112(l) of the House bill, which the conference committee
adopted as the provision governing Utility Units (section 112(n)(1)(A).
It is hard to conceive that Congress would have adopted section
112(n)(1)(A), yet retained the Senate amendment to section 111(d).
While it appears that the Senate amendment to section 111(d) is a
drafting error and therefore should not be considered, we must attempt
to give effect to both the House and Senate amendments, as they are
both part of the current law.
The House and Senate amendments conflict in that they provide
different standards as to the scope of EPA's authority to regulate
under section 111(d). As we explained at proposal, in an effort to give
some effect to both amendments, we reasonably interpret the amendments
as follows: Where a source category is being regulated under section
112, a section 111(d) standard of performance cannot be established to
address any HAP listed under section 112(b) that may be emitted from
that particular source category. Thus, if EPA is regulating source
category X under section 112, section 111(d) could not be
[[Page 16032]]
used to regulate any HAP emissions from that particular source
category. This is a reasonable interpretation of the amendments to
section 111(d) because it gives some effect to both amendments. First,
it gives effect to the Senate's desire to focus on HAP listed under
section 112(b), rather than applying the section 111(d) exclusion to
non-HAP emitted from a source category regulated under section 112,
which a literal reading of the House amendment would do. Second, it
gives effect to the House's desire to increase the scope of EPA's
authority under section 111(d) and to avoid duplicative regulation of
HAP for a particular source category. See 136 Cong. Rec. H12911, 12934
(daily ed. Oct. 26, 1990) (the conferees adopted section 112(n)(1)(A)
``because of the logic of basing any decision to regulate on the
results of scientific study and because of the emission reductions that
will be achieved and the extremely high costs that electric utilities
will face under other provisions of the new Clean Air Act
amendments.'').
We recognize that our proposed reconciliation of the two
conflicting amendments does not give full effect to the House's
language, because a literal reading of the House language would mean
that EPA could not regulate HAP or non-HAP emitted from a source
category regulated under section 112. Such a reading would be
inconsistent with the general thrust of the 1990 amendments, which, on
balance, reflects Congress' desire to require EPA to regulate more
substances, not to eliminate EPA's ability to regulate large categories
of pollutants like non-HAP. Furthermore, EPA has historically regulated
non-HAP under section 111(d), even where those non-HAP were emitted
from a source category actually regulated under section 112. See, e.g.,
40 CFR 62.1100 (California State Plan for Control of Fluoride Emissions
from Existing Facilities at Phosphate Fertilizer Plants). We do not
believe that Congress sought to eliminate regulation for a large
category of sources in the 1990 Amendments and our proposed
interpretation of the two amendments to section 111(d) avoids this
result.\63\
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\63\ The first instance in which the Agency proposed an
interpretation of the conflicting House and Senate amendments to CAA
section 111(d) was in the January 2004 proposed rule. We recognize
that we may have made statements concerning section 111(d), since
the 1990 Amendments, but those statements did not recognize or
account for the two different amendments to section 111(d), as
enacted in 1990. We are also amending 40 CFR 60.21, as part of the
final CAMR. That regulation, which was promulgated in 1975,
interprets the 1970 CAA and defines a ``designated pollutant'' for
purposes of section 111(d), as excluding any pollutant that is
listed on the section 112(b)(1)(A) list. There is no section
112(b)(1)(A) in the current act, as amended in 1990. We are
therefore revising 40 CFR 60.21 because it does not reflect the
current language of section 111(d), as amended in 1990.
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Finally, in assessing whether to revise the December 2000
``necessary'' finding, it is reasonable to look to whether CAA section
111 constituted a viable alternative authority for regulating utility
HAP emissions prior to the December 2000 finding. The answer is yes and
therefore under our proposed interpretation of the conflicting
amendments, we could have regulated HAP from Utility Units under
section 111(d). We listed coal- and oil-fired Utility Units under
section 112(c) in December 2000 based solely on our appropriate and
necessary finding. As explained above, that finding lacks foundation
and recent information confirms that it is neither appropriate nor
necessary to regulate Utility Units under CAA section 112. We should
have recognized prior to the December 2000 finding that section 111
constituted a viable authority for regulating utility HAP emissions and
therefore should have never listed Utility Units on the Section 112(c)
list. In addition, as explained below, the December 2000 finding and
associated listing is not a final agency action and EPA can therefore
make revisions to that finding at any point prior to taking final
action. Such revisions are particularly appropriate here, because the
prior finding is incorrect and new information confirms this fact.
Some commenters argue that their reading of the House amendment and
reconciliation of the amendments is reasonable, but the question is not
whether commenters have identified a reasonable construction of section
112(d). Rather, the issue is whether our construction is a permissible
one, and for the reasons set forth above, we believe that it is. See
Smiley v. Citibank, N.A. 517 U.S. 735, 744-45 (1996) (a ``permissible''
interpretation is one that is ``reasonable''). Other commenters
effectively ask us to ignore the House amendment because the Senate
amendment reflects the law as of 1977. We cannot ignore the House
amendment, as it is part of current law, and Congress substantially
amended the law in 1990, by including, among other things, section
112(n)(1)(A).\64\
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\64\ Finally, some commenters argue that EPA's interpretation of
the conflicting amendments was unreasonable, because it would give
EPA discretion to regulate area sources, under section 111, as
opposed to section 112. These commenters fail to recognize the
listing criteria for area sources under section 112(c)(3). That
section, for example, provides that EPA shall list a category or
subcategory of area sources under section 112 if it finds that the
category or subcategory presents a threat of adverse effects to
human health or the environment in a manner ``that warrants
regulation under section 112.'' Thus, EPA must determine whether the
category or subcategory presents a threat that warrants regulation
under section 112. If EPA determined that the listing criteria for a
category of area sources were not met, nothing would preclude EPA
from regulating HAP from that category under section 111(d), which
contains different requirements for regulation. See General Overview
of section 111 above.
Another commenter argued that EPA's interpretation of the two
amendments is contrary to a canon of statutory construction that
provides that where a conflict exists between two provisions of an
act, the last provision in point of arrangement controls. This
commenter argues that because the Senate conforming amendment is
found in section 302 of Public Law 101-549, and the House amendment
in section 108(g), the Senate amendment should control. As explained
above, this canon of statutory construction is not directly relevant
to situations where the conflict at issue is between two different
amendments to the same statutory provision. Furthermore, application
of this canon of construction would be contrary to the legislative
history described above.
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VIII. Removal of Coal- and Oil-Fired Utility Units From the Section
112(C) List
Section 112(n)(1)(A) sets forth the criteria for regulating Utility
Units under section 112. The criteria are: Whether regulation of
Utility Units under section 112 of the CAA is ``appropriate'' and
``necessary.'' In December 2000, EPA added coal- and oil-fired Utility
Units to the section 112(c) list in light of its positive appropriate
and necessary finding for such units. See 65 FR 79831.
In the January 2004 proposed rule, EPA proposed removing coal- and
oil-fired Utility Units from the section 112(c) list based on our
proposed reversal of the December 2000 finding. Today, we conclude that
the December 2000 finding lacked foundation and that regulation of
coal- and oil-fired Utility Units under section 112 is not appropriate
and necessary. Based on those decisions and our revision of the
December 2000 finding, we remove coal- and oil-fired Utility Units from
the section 112(c) list. We disagree with those commenters that argue
that EPA cannot remove coal and oil-fired Utility Units from the
section 112(c) list without satisfying the delisting criteria in
section 112(c)(9).
EPA reasonably interprets section 112(n)(1)(A) as providing it
authority to remove coal- and oil-fired units from the section 112(c)
list at any time that it makes a negative appropriate and necessary
finding under the section. Congress set up an entirely different
structure and predicate for assessing whether Utility Units should be
listed for regulation under section 112. Compare 112(c)(1) and (c)(3),
with 112(n)(1)(A). Section 112(n)(1)(A)
[[Page 16033]]
therefore occupies the field in section 112 with regard to Utility
Units. Section 112(n)(1)(A) provides EPA significant discretion in
making the appropriate and necessary finding and nothing in section
112(n)(1)(A) suggests that EPA cannot revise its finding, where, as
here, it has both identified errors in its prior finding and determined
that the finding lacked foundation, and where EPA has received new
information that confirms that it is not appropriate or necessary to
regulate coal- and oil-fired Utility Units under section 112.\65\
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\65\ Although not critical to our analysis, we do note that it
is questionable whether we even had a legal obligation in December
2000 to list Utility Units under section 112(c) after making the
positive appropriate and necessary finding. Section 112(n)(1)(A)
makes no reference to CAA section 112(c) and the framework of
section 112(c)(1) and (c)(3) does not expressly provide for the
listing of Utility Units. Rather, those provisions speak to major
and area sources, which Congress treated differently from Utility
Units.
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The section 112(c)(9) criteria also do not apply in two situations
that are directly relevant here. First, the December 2000 appropriate
and necessary finding and associated listing are not final agency
actions. UARG v. EPA, 2001 WL 936363, No. 01-1074 (DC Cir. July 26,
2001). EPA therefore has inherent authority under the CAA to revise
those actions at any time based on either identified errors in the
December 2000 finding or on new information that bears upon that
finding. Second, as explained in the proposed rule, the section
112(c)(9) criteria do not apply where, as here, the source category at
issue did not meet the statutory criteria for listing at the time of
listing. See 68 FR 28197, 28200 June 4, 1996; see also 69 FR 4689
(citing additional examples where EPA has removed a source category
from the section 112(c) list without following the criteria in section
112(c)(9) due to an error at the time of listing). For all of the
reasons noted above, EPA did not meet the statutory listing criteria at
the time of listing for coal- and oil-fired Utility Units. Accordingly,
coal- and oil-fired Utility Units should never have been listed under
section 112(c) and therefore the criteria of section 112(c)(9) do not
apply to today's action.
IX. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review
Under Executive Order 12866 (58 FR 51735, October 4, 1993), the
Agency must determine whether a regulatory action is ``significant''
and therefore subject to Office of Management and Budget (OMB) review
and the requirements of the Executive Order. The Order defines
``significant regulatory action'' as one that is likely to result in a
rule that may:
1. Have an annual effect on the economy of $100 million or more or
adversely affect in a material way the economy, a sector of the
economy, productivity, competition, jobs, the environment, public
health or safety, or State, local, or Tribal governments or
communities;
2. Create a serious inconsistency or otherwise interfere with an
action taken or planned by another agency;
3. Materially alter the budgetary impact of entitlements, grants,
user fees, or loan programs or the rights and obligations of recipients
thereof; or
4. Raise novel legal or policy issues arising out of legal
mandates, the President's priorities, or the principles set forth in
the Executive Order.
Pursuant to the terms of Executive Order 12866, OMB has notified us
that it considers this a ``significant regulatory action'' within the
meaning of the Executive Order. We have submitted this action to OMB
for review. However, EPA has determined that this rulemaking will not
have a significant economic impact. Changes made in response to OMB
suggestions or recommendations will be documented in the public record.
All written comments from OMB to EPA and any written EPA response to
any of those comments are included in the docket listed at the
beginning of this notice under ADDRESSES.
B. Paperwork Reduction Act
This action does not contain any information collection
requirements and therefore is not subject to the Paperwork Reduction
Act (44 U.S.C. 3501 et seq.).
C. Regulatory Flexibility Act
The Regulatory Flexibility Act (5 U.S.C. 601 et seq.) (RFA), as
amended by the Small Business Regulatory Enforcement Fairness Act (Pub.
L. 104-121) (SBREFA), provides that whenever an agency is required to
publish a general notice of rulemaking, it must prepare a regulatory
flexibility analysis, unless it certifies that the rule, if
promulgated, will not have ``a significant economic impact on a
substantial number of small entities.'' 5 U.S.C. 605(b). Small entities
include small businesses, small organizations, and small governmental
jurisdictions.
As was discussed in the January 30, 2004 NPR, EPA determined that
it was not necessary to prepare a regulatory flexibility analysis in
conjunction with this rulemaking. We certify that this action will not
have a significant impact on a substantial number of small entities
because it imposes no regulatory requirements.
D. Unfunded Mandates Reform Act
Title II of the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-
4) (UMRA), establishes requirements for Federal agencies to assess the
effects of their regulatory actions on State, local, and Tribal
governments and the private sector. Under UMRA section 202, 2 U.S.C.
1532, EPA generally must prepare a written statement, including a cost-
benefit analysis, for any proposed or final rule that ``includes any
Federal mandate that may result in the expenditure by State, local, and
Tribal governments, in the aggregate, or by the private sector, of
$100,000,000 or more * * * in any one year.'' A ``Federal mandate'' is
defined under section 421(6), 2 U.S.C. 658(6), to include a ``Federal
intergovernmental mandate'' and a ``Federal private sector mandate.'' A
``Federal intergovernmental mandate,'' in turn, is defined to include a
regulation that ``would impose an enforceable duty upon State, local,
or Tribal governments,'' section 421(5)(A)(i), 2 U.S.C. 658(5)(A)(i),
except for, among other things, a duty that is ``a condition of Federal
assistance,'' section 421(5)(A)(i)(I). A ``Federal private sector
mandate'' includes a regulation that ``would impose an enforceable duty
upon the private sector,'' with certain exceptions, section 421(7)(A),
2 U.S.C. 658(7)(A).
We have determined that the final rule does not contain a Federal
mandate that may result in expenditures of $100 million or more for
State, local, or tribal governments, in the aggregate, or the private
sector in any 1 year. Thus, today's final rule is not subject to the
requirements of sections 202 and 205 of the UMRA. In addition, we have
determined that the final rule contains no regulatory requirements that
might significantly or uniquely affect small governments because it
contains no regulatory requirements that apply to such governments or
impose obligations upon them. Therefore, the final rule is not subject
to the requirements of section 203 of UMRA.
E. Executive Order 13132: Federalism
Executive Order 13132, entitled ``Federalism'' (64 FR 43255, August
10, 1999), requires EPA to develop an accountable process to ensure
``meaningful and timely input by State and local officials in the
development of regulatory policies that have federalism implications.''
``Policies that have federalism implications'' is defined in the EO to
include regulations that have
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``substantial direct effects on the States, on the relationship between
the national government and the States, or on the distribution of power
and responsibilities among the various levels of government.''
This rule does not have federalism implications. It will not have
substantial direct effects on the States, on the relationship between
the national government and the States, or on the distribution of power
and responsibilities among the various levels of government, as
specified in EO 13132. The CAA establishes the relationship between the
Federal government and the States, and this rule does not impact that
relationship. Thus, EO 13132 does not apply to this rule. However, in
the spirit of EO 13132, and consistent with EPA policy to promote
communications between EPA and State and local governments, EPA
specifically solicited comment on this rule from State and local
officials.
F. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments
EO 13175, entitled ``Consultation and Coordination with Indian
Tribal Governments'' (65 FR 67249, November 9, 2000), requires EPA to
develop an accountable process to ensure ``meaningful and timely input
by Tribal officials in the development of regulatory policies that have
Tribal implications.''
This rule does not have Tribal implications as defined by EO 13175.
It does not have a substantial direct effect on one or more Indian
Tribes, in that it is a determination not to regulate utilities under
section 112, and therefore imposes no burdens on tribes. Furthermore,
this rule does not affect the relationship or distribution of power and
responsibilities between the Federal government and Indian Tribes. The
CAA and the Tribal Authority Rule (TAR) establish the relationship of
the Federal government and Tribes in implementing the Clean Air Act.
Because this rule does not have Tribal implications, EO 13175 does not
apply.
Although EO 13175 does not apply to this rule, EPA took several
steps to consult with Tribal officials in developing this rule. EPA
gave a presentation to a national meeting of the Tribal Environmental
Council (NTEC) in April 2001, and encouraged Tribal input at an early
stage. EPA then worked with NTEC to find a Tribal representative to
participate in the workgroup developing the rule, and included a
representative from the Navajo Nation as a member the official
workgroup, with a representative from the Campo Band later added as an
alternate. In March 2004, EPA provided a briefing for Tribal
representatives and the newly formed National Tribal Air Association
and NTEC. EPA received comments on this rule from a number of tribes,
and has taken those comments and other input from Tribal
representatives into consideration in development of this rule.
G. Executive Order 13045: Protection of Children From Environmental
Health and Safety Risks
Executive Order 13045, ``Protection of Children from Environmental
Health and Safety Risks'' (62 FR 19885, April 23, 1997) applies to any
rule that (1) is determined to be ``economically significant'' as
defined under EO 12866, and (2) concerns an environmental health or
safety risk that EPA has reason to believe may have a disproportionate
effect on children. If the regulatory action meets both criteria,
section 5-501 of the EO directs the Agency to evaluate the
environmental health or safety effects of the planned rule on children,
and explain why the planned regulation is preferable to other
potentially effective and reasonably feasible alternatives considered
by the Agency.
The final rule is not subject to Executive Order 13045 because it
is not an economically significant regulatory action as defined by
Executive Order 12866. In addition, EPA interprets Executive Order
13045 as applying only to those regulatory actions that are based on
health and safety risks, such that the analysis required under section
5-501 of the Executive Order has the potential to influence the
regulations. The final rule is not subject to Executive Order 13045
because it does not include regulatory requirements based on health or
safety risks.
Nonetheless, in making its determination as to whether it is
``appropriate and necessary'' to regulate Utility Units under section
112, EPA considered the effects of utility HAP emissions on both the
general population and sensitive subpopulations, including children.
H. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
Executive Order 13211 (66 FR 28355, May 22, 2001) provides that
agencies shall prepare and submit to the Administrator of the Office of
Regulatory Affairs, OMB, a Statement of Energy Effects for certain
actions identified as ``significant energy actions.'' Section 4(b) of
EO 13211 defines ``significant energy actions'' as ``any action by an
agency (normally published in the Federal Register) that promulgates or
is expected to lead to the promulgation of a final rule or regulation,
including notices of inquiry, advance notices of final rulemaking, and
notices of final rulemaking: (1) (i) That is a significant regulatory
action under EO 12866 or any successor order, and (ii) is likely to
have a significant adverse effect on the supply, distribution, or use
of energy; or (2) that is designated by the Administrator of the Office
of Information and Regulatory Affairs as a ``significant energy
action.'' Although this final rule is a significant regulatory action
under EO 12866, it will not have a significant adverse effect on the
supply, distribution, or use of energy.
I. National Technology Transfer and Advancement Act
Section 12(d) of the National Technology Transfer and Advancement
Act (NTTAA) of 1995 (Pub. L. 104-113; Section 12(d), 15 U.S.C. 272
note) directs EPA to use voluntary consensus standards (VCS) in their
regulatory and procurement activities unless to do so would be
inconsistent with applicable law or otherwise impractical. Voluntary
consensus standards are technical standards (e.g., materials
specifications, test methods, sampling procedures, business practices)
developed or adopted by one or more voluntary consensus bodies. NTTAA
directs EPA to provide Congress, through annual reports to OMB, with
explanations when an agency does not use available and applicable VCS.
This action does not involve technical standards and therefore the
NTTAA does not apply.
J. Executive Order 12898: Federal Actions To Address Environmental
Justice in Minority Populations and Low-Income Populations
Executive Order 12898, ``Federal Actions to Address Environmental
Justice in Minority Populations and Low-Income Populations,'' provides
for Federal agencies to consider the impact of programs, policies, and
activities on minority populations and low-income populations,
including tribes.
As described above, in making its determination as to whether it is
``appropriate and necessary'' to regulate Utility Units under section
112, EPA considered the effects of utility HAP emissions on both the
general population and sensitive subpopulations, including subsistence
fish-eaters. EPA's analysis considered such subpopulations as the
Chippewa in Minnesota, Wisconsin, and Michigan; and the Hmong in
Minnesota and
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Wisconsin. As explained above, the Agency has concluded that it is not
``appropriate and necessary'' to regulate Utility Units under section
112, in light of all available information, including information on
subsistence fish-eaters. The Agency believes that implementation of the
CAIR and, independently, the CAMR will remove the hazards to public
health resulting from utility HAP emissions.
This action, however, does not actually regulate HAP emissions from
utilities. The CAMR does regulate Hg emissions from utilities, and it
is in the CAMR rulemaking that EPA has addressed the impacts of that
regulation on the populations addressed by Executive Order 12898.
K. Congressional Review Act
The Congressional Review Act, 5 U.S.C. 801 et seq., as added by
SBREFA of 1996, generally provides that before a rule may take effect,
the agency promulgating the rule must submit a rule report, which
includes a copy of the rule, to each House of the Congress and to the
Comptroller General of the U.S. The EPA will submit a report containing
this rule and other required information to the U.S. Senate, the U.S.
House of Representatives, and the Comptroller General of the U.S. prior
to publication of the rule in the Federal Register. The final rule is
not a ``major rule'' as defined by 5 U.S.C. 804(2). The final rule will
be effective on March 29, 2005.
Dated: March 15, 2005.
Stephen Johnson,
Acting Administrator.
[FR Doc. 05-6037 Filed 3-28-05; 8:45 am]
BILLING CODE 6560-50-P